Allah, the Exalted, said:
٢٥١ - باب فضل الدعاء بظهر الغيب
Allah, the Exalted, said:
And [there is a share for] those who come after them, saying, "Our Lord, forgive us and our brothers who preceded us in faith and put not in our hearts [any] resentment toward those who have believed. Our Lord, indeed You are Kind and Merciful."
And Allah, the Exalted, said:
So know, [O Muḥammad], that there is no deity except Allāh and ask forgiveness for your sin1 and for the believing men and believing women. And Allāh knows of your movement and your resting place.
And Allah, the Exalted, said, relating about Ibrahim (peace and blessings be upon him):
Our Lord, forgive me and my parents and the believers the Day the account is established."
On the authority of Abu al-Darda (may Allah be pleased with him): that he heard the Messenger of Allah ﷺ say: "There is no Muslim servant who supplicates for his brother in his absence but that the angel says: And for you the like." Narrated by Muslim.
And on his authority: that the Messenger of Allah ﷺ used to say: "The supplication of a Muslim person for his brother in his absence is answered. At his head is an appointed angel; whenever he supplicates for his brother with good, the angel appointed over him says: Amin, and for you the like." Narrated by Muslim.