What if the parents are non-Muslim?
Islam is such a complete code of life in which the rights of everyone have been detailed. Islam has detailed not only the rights of human beings but also that of animals. In regard to rights, there is no discrimination between Muslims and non-Muslims. Thus, even if someone’s parents are non-Muslim, Islam still orders that they should be treated kindly. Almighty Allah says in the Holy Quran:
And if both of them contend with you that you should associate (others) with Me, of which you have no knowledge, then do not obey them. And cooperate with them in worldly affairs in a decent manner. But (in the matter of faith and the Last Hour and the related affairs) follow someone who adopts the path of turning to Me in repentance and submitting to My injunctions. Then you are to return to Me alone. So I shall inform you about the works that you used to do. Surah Luqman (31:15)
There is a Hadith in Sahih Bukhari:
Translation: Hadhrat Hishaam bin ‘Urwa (May Allah be well pleased with him) narrates on the authority of his father that Hadhrat Asma bint Abu Bakr told him: In the era of the Holy Prophet (Sallallahu alaihi wa sallam), my mother came to me in the hope that I will take care of her. I asked the Holy Prophet (Sallallahu alaihi wa sallam): Can I treat her nicely? He said: Yes. Hadhrat Sufyan bin ‘Uyainah (May Allah be well pleased with him) says that this verse of the Holy Quran was revealed about this: Allah does not forbid you to be good to them and treat them with equity and justice who did not fight against you on (the question of) Din (Religion), nor did they drive you out of your homes (i.e., homeland). Surely, Allah likes those who conduct themselves with equity and justice (Surah Mumtahina-08) (Sahih Bukhari, Hadith No. 5979; Sahih Muslim, Hadith No. 2372)
There is a Hadith in Jame’ Ul Ahadeeth and Kanz Ul ‘Ummal:
Translation: It is narrated on the authority of Hadhrat Abu Hurairah (May Allah be well pleased with him) that the Holy Prophet (Sallallahu alaihi wa sallam) said: You don’t walk ahead of your father. Don’t become the cause of abuses for your father. Don’t sit before he sits and don’t address him by his name. (Jame’ Ul Ahadeeth, Hadith No. 16942; Kanz Ul ‘Ummal, 45514)