Muhammad ibn Yaqub, from a number of our companions, from Ahmad ibn Muhammad, from Ali ibn al-Hakam, from Musa ibn Bakr, from Abu Abdillah عليه السلام, peace be upon him: (Imam عليه السلام was asked) regarding ‘a man who made upon himself the fasting of a month, so he fasted fifteen days from it, then an affair occurred for him.’ Imam عليه السلام said: “If he had fasted fifteen days, then he may make up what remains upon him. But if it was less than fifteen days, it would not suffice him until he fasts a complete month.”