Chapter on the Detailed Explanation of Prayer, Including the Obligatory and Recommended, and What is Permissible and Not Permissible.

And from him, from Safwan from Hammad ibn Uthman, who said: I said to Abu Abdillah عليه السلام: "I experience doubt while I am in prostration, and I do not know whether I have performed the rak‘ah or not." Imam عليه السلام said: "You have performed the rak‘ah, continue on."