Musannaf Ibn Abi Shaybah 9361 — Separating the days when making up

Muhammad bin al-Munkadir said: It reached me that the Prophet (peace and blessings be upon him) was once asked whether the making up of Ramadan fasts may be split up and done separately. He said: "Yes, you may do that. Consider: if one of you owed a debt and paid it off one or two dirhams at a time, would the debt not be paid? And Allah Almighty is more forgiving and pardoning."