In the form of reciprocation, showing gratitude to the good things parents have done and treating them as kindly and mercifully as they deserve, Islam put duties on children toward their parents, particularly when parents grow old and become weaker. Allah commands people to be compassionate toward their parents, treat them kindly and mercifully and obey them exactly the same way the parents used to treat their little kids.
On top of parents’ rights is obeying the parents and being compassionate toward the parents. Behind Allah, nobody else except the parents seems to be more compassionate and kind. Due to its importance, Allah when enjoins the duty of being kind and compassionate to their parents in the Quran, this injunction always appears soon after the injunction to worship only one God. Allah exalted He is says in the Quran what means: "Your Lord has commanded that you worship none but Him, and that you be good to your parents. If either of them or both of them reach old age with you, do not say to them a word of disrespect, nor scold them, but say to them kind words. And lower to them the wing of humility, out of mercy, and say, “My Lord, have mercy on them, as they raised me when I was a child.”" (Surah al-Isra, 23,24)