In The Name of Allaah, The Most Merciful, The Bestower of Mercy.
Imaam As-Sadi [rahimahullaah] said:
If these discoveries allied with the religion as its guide, then its benefits would have been twice as great as what is witnessed; its harm and evils would have been repelled and it would have been established upon good and uprightness; its outcomes would have been good and would be a means of rectification in the religious and worldly affairs. 
Shaikh Rabee Bin Haadi [may Allaah preserve him said:
If medicine, engineering and chemistry are not placed below [and regulated by] the knowledge which the Prophets brought, they become nothing; [rather] they will only increase the people in corruption. The knowledge brought by the Prophets is [a means of] rectification for the people [in their religious and worldly affairs], a guide for them towards the right path and removes them from the darkness they are living in – the darkness of kufr and ignorance.
As for the knowledge of the philosophers and the heretics, then what Allaah has stated [i.e. in Surah Ghaafir’ Aayah 83] truly applies to it. [Allaah said]: [فَلَمَّا جَآءَتۡهُمۡ رُسُلُهُم بِٱلۡبَيِّنَـٰتِ فَرِحُواْ بِمَا عِندَهُم مِّنَ ٱلۡعِلۡمِ وَحَاقَ بِهِم مَّا كَانُواْ بِهِۦ يَسۡتَہۡزِءُونَ -Then when their Messengers came to them with clear proofs, they were glad [and proud] with that which they had of the knowledge [of worldly things]: And that at which they used to mock, surrounded them [i.e. the punishment]. [Surah Ghaafir’ Aayah 83]
It is the knowledge which the people boast about nowadays, whether it is medicine, engineering, astronomy, [modern] politics and economics. After the Prophets came to them – to remove them from the darkness of ignorance and enter them into the light of the knowledge [of divine revelation] and Eemaan- they became glad and boastful with the knowledge they possess, [just as Allaah has stated]: [فَلَمَّا جَآءَتۡهُمۡ رُسُلُهُم بِٱلۡبَيِّنَـٰتِ فَرِحُواْ بِمَا عِندَهُم مِّنَ ٱلۡعِلۡمِ وَحَاقَ بِهِم مَّا كَانُواْ بِهِۦ يَسۡتَہۡزِءُونَ -Then when their Messengers came to them with clear proofs, they were glad [and proud] with that which they had of the knowledge [of worldly things]: And that at which they used to mock, surrounded them [i.e. the punishment]. [Surah Ghaafir’ Aayah 83]
[Likewise, Allaah informed us that] Qaaroon said: [إِنَّمَآ أُوتِيتُهُ ۥ عَلَىٰ عِلۡمٍ عِندِىٓۚ – This [i.e. vast wealth] has been given to me only because of knowledge I possess. [Surah Al-Qasas’ Aayah 78]
They [i.e. the people] rebuke him [i.e. Qaaroon] because he did not want to spend from his wealth based on what Allaah has commanded and Allaah’s revelation, so Allaah said that he said: [إِنَّمَآ أُوتِيتُهُ ۥ عَلَىٰ عِلۡمٍ عِندِىٓۚ – This [i.e. vast wealth] has been given to me only because of knowledge I possess. [Surah Al-Qasas’ Aayah 78]
Likewise, Allaah said: [وَإِذَآ أَنۡعَمۡنَا عَلَى ٱلۡإِنسَـٰنِ أَعۡرَضَ وَنَـَٔا بِجَانِبِهِ – And when We bestow Our Grace on man (the disbeliever), he turns away and becomes arrogant, far away from the Right Path. [Surah Al-Israa’ Aayah 83]
[Allaah said]: [ثُمَّ إِذَا خَوَّلۡنَـٰهُ نِعۡمَةً۬ مِّنَّا قَالَ إِنَّمَآ أُوتِيتُهُ ۥ عَلَىٰ عِلۡمِۭۚ بَلۡ هِىَ فِتۡنَةٌ۬ وَلَـٰكِنَّ أَكۡثَرَهُمۡ لَا يَعۡلَمُونَ – Then when We have (rescued him from that harm and) changed it into a favour from Us, he says: “Only because of knowledge (that I possess) I obtained it.” Nay, it is only a trial, but most of them know not! [Surah Az-Zumar’ Aayah 49]
Allaah said that he [i.e. the ungrateful human being says after being rescued from hardship]: [قَالَ إِنَّمَآ أُوتِيتُهُ ۥ عَلَىٰ عِلۡمِۭۚ – he says: “Only because of knowledge (that I possess) I obtained it]; but Allaah said: [ وَلَـٰكِنَّ أَكۡثَرَهُمۡ لَا يَعۡلَمُونَ – Nay, it is only a trial, but most of them know not!]
These sciences become a trial and tribulation if they are not placed below [and regulated by] the knowledge which Muhammad [sallal laahu alayhi wasallam] brought. [Ref 2]
Medical practice is one of the noblest occupations because its subject matter is about the life of the human being. Its aim and purpose is to preserve the health of the human being, strengthen physical well-being and distance a person from illness. The need for medicine is great and a person is in need of it in every situation. That is because one is in need of good health in order to carry out work and fulfil obligations in this life, which is the reason behind the creation of the human being. Allaah [The Most High] said: [وَمَا خَلَقْتُ الْجِنَّ وَالْإِنسَ إِلَّا لِيَعْبُدُونِ – And I (Allah) created not the jinns and humans except they should worship Me (Alone)]. [51:56]
So the aim behind medicine is to preserve health, strengthen the body’s physical wellbeing and distance it from illness. Among the virtues of involvement in healthcare is that it preserves life and this is one of the five necessities which Islaam came to preserve, and they are: Religion; Life; Intellect; Honour (i.e. sexual intercourse through marriage and not outside of it) and Wealth. It helps a Muslim and the society to repel harm. It is well known that the messenger (sallal-laahu-alayhi-wasallam) said: لا ضرر ولا ضرار – There should be neither harming nor reciprocating harm.’’ [Reported by Ibn Maajah 2341; Ahmad 1/313)]
Fulfilment of the obligation of co-operating upon righteousness and piety from another angle. And with regards to this he (or she) fulfils the statement of Allaah: [وَتَعَاوَنُوا عَلَى الْبِرِّ وَالتَّقْوَىٰ – Help you one another in Al-Birr and At-Taqwa (virtue, righteousness and piety) 5:2]
Fulfilment of the command of the Messenger (sallal-laahu-alayhi-wasallam): Usaamah bin Sharik (radiyallaahu-anhu) said: A Bedouin said, O Messenger of Allaah(sallal-laahu-alayhi-wasallam)! Should we seek medical treatment? He (sallal-laahu-alayhi-wasallam) said: seek medical treatment, for Allaah has not created any disease but He has also created a remedy for it, except for one disease: old age.’’ [Reported by Abu Dawud Number 3855]
One should hope for Allaah’s reward and good recompense. Should be sincere to Allaah in such a profession and should not practice medicine only for their status to be acknowledged. Rather one should be sincere and hope for Allaah’s reward. Alqamah Ibn Waqqaas Al-Laythiy said: I heard Umar Ibn Al-khattaab (radiyallaahu-anhu) saying whilst on the minbar:I heard the Messenger of Allaah (sallal-laahu-alayhi-wasallam ) saying:
إنما الأعمال بالنيات وإنما لكل امرئ ما نوى فمن كانت هجرته إلى الله ورسوله فهجرته إلى الله ورسوله ومن كانت هجرته لدنيا يصيبها أو امرأة ينكحها فهجرته إلى ما هاجر إليه
Actions are (judged) by intentions and every person will have what he intended. So he whose migration was to Allah and His Messenger, his migration is to Allah and His Messenger. And he whose migration was for some worldly (gain) or for a woman to marry, then his migration is to that for which he migrated.” [Al-Bukhari and Muslim]
Doctor must fear Allaah with regards to those affairs about which one is consulted, especially that which is related to the rights of the people- such as when a sick person approaches him for a sick note or when in need of a medical note to prove that he is fit for employment, or when consulted regarding a particular type of medication, or whether the state of health of an individual (woman) allows her to utilise contraception in order not to get pregnant, or whether her state of health warrants the removal of her ovaries. It has been reported in a hadeeth by Abu Hurairah (radiyallaahu-anhu) who said that the Messenger (sallal-laahu-alayhi-wasallam) said: [الْمُسْتَشَارُ مُؤْتَمَنٌ – The consultee is in a position of trust] [Reported by Abu Dawud (rahimahullaah)’ Number 5128’ & declared Saheeh by Imaam Albaani (rahimahullaah) in his checking of Sunan Abee Dawud]
Few Reminders From The Above Hadeeth: [الْمُسْتَشَارُ مُؤْتَمَنٌ – The consultee is in a position of trust]
[المستشار -The Consultee]: He is the one whose opinion is sought after regarding an affair of Maslahah (i.e. an affair that will bring about benefit and repel harm). He is in a position of trust with regards to what he is asked and it is not permissible for him to deceive the one who consults him, by concealing the affair that would bring about benefit. [Ref 2: See Hadeeth Number 5062′ Vol 4’ page 259′ in Mirqaat Al-Mafaateeh Sharh Mishkaat Al-Masaabeeh]
This hadeeth is an evidence, showing that the consultee has to (advise) with the course of action and opinion -in relation to the consultation – that which he would do for himself. And it is not permissible that he directs his Muslim brother to something he would not be pleased with for himself. [Source: Awnul Ahadis Samadi, Sharhu Al-Adab Al-Mufrad’ Vol 1′ Hadeeth Number 256′ page 283]
The Muslim doctor should not make the patient a means to experimenting the effectiveness of a medication, especially if he fears that there would be great side effects. That is because this experimentation would negate the honour Allaah has bestowed on the children of Aadam. Allaah [The Most High] said:
وَلَقَدۡ كَرَّمۡنَا بَنِىٓ ءَادَمَ وَحَمَلۡنَـٰهُمۡ فِى ٱلۡبَرِّ وَٱلۡبَحۡرِ وَرَزَقۡنَـٰهُم مِّنَ ٱلطَّيِّبَـٰتِ وَفَضَّلۡنَـٰهُمۡ عَلَىٰ ڪَثِيرٍ۬ مِّمَّنۡ خَلَقۡنَا تَفۡضِيلاً۬
And indeed We have honoured the Children of Adam, and We have carried them on land and sea, and have provided them with At-Taiyibat(lawful good things), and have preferred them above many of those whom We have created with a marked preference. [Surah Al-Is’raa Aayah 70]
This deed [i.e. using the patient as a means to experimenting the effectiveness of a medication] negates the command [given to person to] safeguard the blood of a Muslim. The Prophet [sallal-laahu-alayhi-wasallam] said: A Muslim is the brother of another Muslim, so he should not oppress him, nor should he hand him over to an oppressor. Whoever fulfilled the needs of his brother, Allaah will fulfil his needs; whoever brought his [Muslim] brother out of discomfort, Allaah will bring him out of a discomfort from the discomforts of the Day of Resurrection, and whoever screened a Muslim, Allaah will screen him on the Day of Resurrection. [Bukhaari Hadeeth Number 2442]
If the Muslim doctor is certain that the harm [or side effects] that will result from the medication is lesser than the harm caused by the continuation of the illness, then it is permissible to give the medication based on choosing the lesser harm between two.
The Muslim doctor should ask the scholars regarding affairs that occur in his profession and should not jump into affairs without background knowledge of the Sharee’ah! He should be careful of (Sigmund) Freud’s absurdities, fictitious and false views and should not be deceived by (Charles) Darwin. Abu Hurairah (radiyallaahu-anhu) said that the Prophet (sallal-laahu-alayhi-wasallam) said, ‘’A slave (of Allaah) may utter a word which pleases Allaah, without giving it much importance, and because of that Allaah will raise him to degrees (of reward); a slave (of Allaah) may utter a word (carelessly) which displeases Allaah, without thinking of its gravity, and because of that he will be thrown into the Hell-fire.’’ [Saheeh al-Bukhaari Number 6478]
Brief Rebuttal Against Darwin
The Muslim doctor should be careful of what is transmitted in the medical journals (or textbooks) and he should not accept everything transmitted in them without ascertaining its correctness, for indeed knowledge is established either through a trustworthy transmission or an unquestionable view point. The affairs of medicine attributed to the Prophet (sallal-laahu-alayhi-wasallam) should be checked as to whether their chains of transmission are authentic, and the affairs of medicine that are established by way of opinions [i.e. through study and research etc] should be examined to find out whether they are [sound, unsound, or whether they contain flaws, sin, offence etc]. He should not be an easy and legitimate prey whom the enemies of Allaah use as a path to transmit that which opposes the Religion of Islaam and causes harm to the Muslims; rather he should know that everything that comes to him regarding modern medicine has to be subjected to research and has to be ascertained.
Doctor should believe that his knowledge of medicine is nothing else but only a means (of cure). As for the effects and effectiveness (of the cure), it is decided by Allaah (The Mighty and Majestic) if He (Allaah) wishes to give cure and well-being. Allaah (The Most High) stated (that Ibraaheem- alayhis-salaam said): [وَإِذَا مَرِضْتُ فَهُوَ يَشْفِينِ – And when I (i.e. Ibraaheem) am ill, it is He (Allaah) who cures me]. [26:80] So Allaah is the one who gives cure and not others. The doctor should make this known to the patient.
He should be pleased with the Divine Will and Decree of Allaah. Abdullaah Ibn Abbaas (radiyallaahu-anhumaa) said: Once I was riding behind the Prophet (sallal-laahu-alayhi-wasallam), so he said: ”O young man, I shall teach you some words (of advice). Be mindful of Allaah, and Allaah will protect you. Be mindful of Allaah, and you will find Him in front of you. If you ask, ask Allaah (Alone). If you seek help, seek help from Allaah (alone). Know that if the nation were to gather together to benefit you with something, they would not benefit with anything except that which Allaah has already recorded for you. If they gather to harm you by something, they would not be able to harm you by anything except what Allaah has already recorded against you. The pens have been lifted and the pages have dried’’. [Recorded by Tirmidhee who said it is a Hasan saheeh hadith. Number 20516]
So neither should a doctor be beguiled by his (or her) knowledge of medicine nor should he (or she) make objections to the power and position of his (or her) Lord (Allaah). He (or she) should know that the affairs of the creation alternate based on Allaah’s (The Most High) decrees. [Re 3]
[Ref 1: Source: Ad-Dalaa’il Al-Qur’aaniyyah Fee Annal Uloom Wal-A’maal An-Naafi’ah Al-Asriyyah Daakhilatun Fid-deen Al-Islaamiy 44]
[Ref 2: An Excerpt from Marhaban Yaa Taalibal Ilm. Page 100]
[Ref 3: Excerpts from Akhlaaq At-Tabeeb Al-Muslim pages 4- 18]