6. A number of our people have narrated from Ahmad ibn Muhammad from Ali ibn al-Hakam from Musa ibn Bakr from al-Fudayl who has said the following: “I once asked abu ‘ Abd Allah , about a man who makes it obligatory upon himself to fast one month. He fasts fifteen days then something happens. He (the Imam) said, ‘If he has fasted fifteen days he completes (compensatory fast) of the rest but if it is less than fifteen days, it is not sufficient until he fasts one whole month.”’