The believer should not make friends with anyone but a believer and he should not take as a close friend anyone but a monotheist (haneef), because the Prophet (blessings and peace of Allah be upon him) said, “Do not keep company with anyone but a believer and do not let anyone eat your food except one who is pious.”
Narrated by al-Tirmidhi (2395); classed as hasan by al-Albaani in Saheeh al-Tirmidhi.
Making friends with disbelievers has a negative impact on the believer, because he may be influenced by some of his religious customs or it may lead to a weakening in his heart of the principle of befriending or supporting believers and disavowing disbelievers (al-wala’ wa’l-bara’), or he may fail to denounce in his heart this person or those who follow his religion, because of frequently mixing with them and getting used to them.
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) was asked about the ruling on mixing with kaafirs and treating them kindly in the hope that they might become Muslim.
He replied: There is no doubt that the Muslim is obliged to hate the enemies of Allah and disavow them, because this is the way of the Messengers and their followers. Allah, may He be exalted, says (interpretation of the meaning):
“Indeed there has been an excellent example for you in Ibraaheem (Abraham) and those with him, when they said to their people: ‘Verily, we are free from you and whatever you worship besides Allaah, we have rejected you, and there has started between us and you, hostility and hatred for ever until you believe in Allaah Alone’”
“You (O Muhammad صلى الله عليه وسلم) will not find any people who believe in Allaah and the Last Day, making friendship with those who oppose Allaah and His Messenger (Muhammad صلى الله عليه وسلم), even though they were their fathers or their sons or their brothers or their kindred (people). For such He has written Faith in their hearts, and strengthened them with Rooh (proofs, light and true guidance) from Himself”
Based on that, it is not permissible for a Muslim to feel love in his heart for the enemies of Allah who in fact are also enemies to him. Allah, may He be exalted, says (interpretation of the meaning):
“O you who believe! Take not My enemies and your enemies (i.e. disbelievers and polytheists) as friends, showing affection towards them, while they have disbelieved in what has come to you of the truth”
With regard to the Muslim treating them kindly and gently in the hope that they will become Muslim and believe, there is nothing wrong with this, because it comes under the heading of softening the hearts towards Islam. But if there is no hope of that, then he should treat them as they deserve to be treated. This is discussed in detail in the books of the scholars, especially the book Ahkaam Ahl al-Dhimmah by Ibn al-Qayyim (may Allah have mercy on him). End quote.
Majmoo‘ Fataawa Ibn ‘Uthaymeen (3/31)
There is nothing wrong with giving Zamzam water to a sick kaafir for the purpose of healing, or with treating him if one is a doctor, or with helping him if he is sick and in need, or with visiting him when he is sick. There is nothing wrong with any of that, especially if there is the hope that this will soften his heart towards Islam or if that kaafir deserves it because of some previous kindness that he showed, or other praiseworthy purposes.
It is proven in al-Bukhaari (2276) and Muslim (2201) that Abu Sa‘eed al-Khudri (may Allah be pleased with him) treated the chief of a tribe who had been stung by a scorpion with ruqyah by reciting al-Faatihah, and he recovered, and his people were mushrikeen. There is no doubt about the sanctity of the Qur’aan, and that treating a kaafir with ruqya by reciting Qur’aan is a more serious matter than simply giving him Zamzam water to drink or as a remedy.
It says in al-Mawsoo‘ah al-Fiqhiyyah (13/34): There is no difference of opinion among the fuqaha’ that it is permissible for a Muslim to treat a kaafir with ruqya, and they quoted as evidence the hadeeth of Abu Sa‘eed al-Khudri (may Allah be pleased with him) quoted above. The point here is that the tribe with whom they halted and from whom they sought hospitality, but they refused to give them any hospitality, were kaafirs, but the Prophet (blessings and peace of Allah be upon him) did not object to him doing that. End quote.
And Allah knows best.