Explanation of the obligation towards parents

"So your Lord has decreed: Do not worship anyone but Him, and be good to your parents. If one or both of them grow old in your presence, do not say fie to them, nor reprove them, but say gentle words to them

"And look after them with kindness and love, and say: "O Lord, have mercy on them as they nourished me when I was small."

Your Lord knows what is in your heart. If you are righteous, then He is indeed forgiving to those who turn (to Him) in repentance.