Silsilat al-Ahadith al-Sahihah

It is narrated from Sayyiduna Anas (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Allah Almighty will certainly fulfill the promise of reward and recompense He has made to a person for his good deeds. And as for the person to whom He has promised punishment for his bad deeds, then (regarding him) He has the choice (if He wills, He may punish him and fulfill the promise, and if He wills, He may completely forgive him)."