And from him, from Ali bin Ibrahim, from his father, from Hammad, from Hariz, from Muhammad bin Muslim, who said: I asked Abu Abdillah عليه السلام, peace be upon him, about a man who is praying and does not know whether he prayed one rak‘ah or two. Imam عليه السلام said: "He should start over until he is certain that he has completed (the prayer), and this applies in Jumu‘ah, in Maghrib, and in prayer during travel."