Prayer: Realising Body Impurity During Prayer When Time is Short
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 793
If a person starts performing a prayer when time is short, and during it realises that his body has become impure, and he deems it probable that it became impure after he started his prayer, then, in case washing his body would not break up the prayer, he must wash his body. If it would break up the prayer, he must complete it just as he is, and it will be valid.