How Many People Saw Muhammad صلى الله عليه وسلم Pray?
Tawatur itself is the most reliable source. A very large number of sahaba spread across different geographic regions offering salat the same way without any gaps in time – what else could be a more reliable source than this? As I and Umer Qureshi sahab have explained to you many times before, we trace tawatur from today back in time and look for any corruptions or innovations. If we don’t find any then tawatur is established. We can refer to books for fiqh for different time periods for the purpose of verification.