Sayyiduna Ibn Abbas (may Allah be pleased with them both) narrated that a man came to the Prophet (peace and blessings be upon him) and said: O Messenger of Allah, my mother has died and she owed a month of fasting; shall I make it up on her behalf? He (peace and blessings be upon him) said: "If your mother had owed a debt, would you have paid it off?" He said: Yes. He (peace and blessings be upon him) said: "Then the debt of Allah is more deserving of being paid." Sulayman (al-A'mash) (may Allah have mercy on him) said: When Muslim narrated this hadith, while we were all sitting together, al-Hakam and Salamah bin Kuhayl (may Allah have mercy on them both) said: We heard Mujahid (may Allah have mercy on him) mention this hadith from Sayyiduna Ibn Abbas (may Allah be pleased with them both).
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12278