Hazrat Ibn Buraidah narrates from his father that I was sitting in the blessed service of the Prophet (peace and blessings be upon him) when a woman came and said: "My mother had two months of fasts (obligatory) upon her. Can I fast on her behalf?" The Prophet (peace and blessings be upon him) said: "You should fast on her behalf. Tell me, if your mother had a debt and you paid it off, would that be sufficient?" She replied: "Why not." The Prophet (peace and blessings be upon him) said: "Then you should fast on her behalf."