The Quran has this to say regarding parents:

At several places the Quran exhorts us to be on our best behaviour with parents, to pay their dues, and, even when scolded by them, to refrain from angry retorts; we should never be found lacking in loving them or in serving them. That is to say: we should at all times conduct ourselves with the utmost propriety, regardless of how our parents treat us.

According to a hadith a man approached the Prophet and asked, “O Prophet, who is more deserving of my good behaviour?” The Prophet said, “Your mother.” The man then asked, “Who after that?” The Prophet again said, “Your mother”. The man again repeated the question and the Prophet again said “Your mother”. When the man asked the Prophet the fourth time, then he said “Your father” (Sahih Muslim, Hadith No. 2548).

There are many traditions which tell us that after God it is to parents that one has obligations more than to anyone else. One reason for this is that in this world individuals receive the maximum benefits from parents. As such it is incumbent upon a person when he grows up to serve his parents to the best of his ability. He should come to their assistance in their old age as they came to his assistance in his childhood.

Another reason is that serving parents enables a person to become a servant of humanity at large, to look at all human beings with love; to honour them and to pay them their dues.

Source: Simple Wisdom