Majma al-Zawaid — Hadith 17503

Sayyiduna Abdullah bin Amr (may Allah be pleased with him) says: "Whoever repents a year before his death, his repentance is accepted; and whoever repents a month before his death, his repentance is accepted." The narrator says: until he mentioned a day, until he mentioned an hour, until he mentioned a brief moment. The narrator says: A man asked: What is your view if he was a disbeliever and then became Muslim? He said: I am only narrating to you what I heard from the Prophet (peace and blessings be upon him).
Ahmad recorded it; its chain contains a narrator who is not named, and the rest of its narrators are thiqat (trustworthy).