Mukhtasar Muslim

It is narrated from Sayyiduna Jundub (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) said: A man said, "By Allah, Allah will not forgive so-and-so." And Allah the Exalted said, "Who is he who swears that I will not forgive so-and-so? I have forgiven him, and I have rendered all the deeds (of the one who swore) null and void."