Even before answering the question, it is important that a Muslim believes and understands that Allah is not only the Lord of the Muslims, He is the Lord of non-Muslims as well. Therefore we must entirely dismiss any notion that Muslims somehow have a monopoly on Allah sub’haanahu wa ta’ala as a Lord. Allah is the Lord of the heavens and the earth and everything in between. That is a fact and is central to the creed of Islam. “Lord of the heavens and the earth and that which is between them. The Merciful” [78:37]. Denying such is considered heresy (kufr) by agreement of all the scholars of Islam combined. There is no animate, or inanimate being or object in this universe, dead or alive, created or not yet created to our knowledge except that Allah is its Lord. So let’s get that out the way.
Making du’aa, or supplicating to Allah for or on behalf of a non-Muslim is permissible in any affairs of the dunya except according to some scholars, if they are active enemy combatants. Specifically if you’re making du’aa that Allah guides them, give them tawfiq (success) to the deen, or to soften their hearts, in which case you can make that du’aa even for a enemy combatant who is an idolater. Ibn Hajar al-Haytami (died 1556 CE), in his book, Tuhfatul Muh’taaj says that it is permissible for a Muslim to make du’aa for a kaafir (unbeliever) for good health, or for guidance. Making du’aa that a non-Muslim be guided to Islam is mustahabb (recommended). There is no disagreement about that amongst the scholars of Islam.
Abdullah Ibn Umar reported: The Messenger of Allah, peace and blessings be upon him, said, “O Allah, strengthen Islam with one of two men whom you love more: Abu Jahl or Umar ibn al-Khattab.” Ibn Umar said, “The most beloved of the two was Umar.” [at-Tirmithi]. Sometimes the Prophet (SAWS) used to pray against the unbelievers, and sometimes he used to pray for them, as mentioned by ibn Hajar al-As’alaani (died 1449 CE), in Fat’h al-Baari. This was depending upon the circumstance. If he was at war with a particular group of non-Muslims, he wasn’t likely to pray for their long life and increase in their wealth. However if it was under peaceful and amicable circumstances then there is no harm in praying for a non-Muslim in the general affairs of the dun’ya. Likewise, it is no harm for you to say to your relative, co-worker, or neighbor for example, who might be sick; “may Allah heal you, or may Allah make it easy on you, or give you good health, or may Allah protect you, or may Allah guide you to Islam, or anything in that vein.
Al-Bayhaqi (died 1066 CE) relates in Shu’bul Eemaan about a Jewish man who milked a goat and gave some to the Prophet (SAWS) and the Prophet said, “may Allah make you beautiful and make your hair black“, (i.e.) give you good health.
The well-known early scholar of hadith, Ibn Abi Shayba (died 849 CE) had a section in his famous “al–Musannaf” entitled ‘Section regarding du’aa for a idolater‘ where he mentions a narration of Ibrahim an-Nakhi (died 714 CE); that, “A Jewish man came to the Prophet (SAWS) and said, “pray for me”. The Prophet (SAWS) said, “May Allah increase you in your wealth, your children, give you good health and a long life“. Furthermore, Ibrahim an-Nakh’i holds the view that there is no harm in praying for a Christian or a Jew.
The overwhelming majority of the companions of the Prophet were converts to Islam. They had parents, children, cousins, aunts and uncles, relatives, clan embers and neighbors who were all non-Muslim. It is inconceivable that they never prayed for their health, well being, prosperity, overcoming a difficulty, or their guidance to Islam. I don’t know of anyone of the people of knowledge who has ever said that you cannot pray for an unbeliever except for one who clearly died in a state of unbelief, in which case it is not permissible to ask Allah for their forgiveness. And Allah knows best.
Abu Laith Luqman Ibn Abdulkarim Muhammad Ahmad