Hassan was asked: If a man's ablution breaks at the time of Friday prayer, and when he returns after performing ablution, the Imam has already led the prayer, what should he do? Hassan replied that he should pray four rak'ahs.

Hazrat Waki’ says that I asked Hazrat Sufyan: If a person started the Friday prayer with the Imam, but his ablution broke and he went to perform ablution, and when he returned the Imam had finished the prayer, what should he do now? He replied: If he has not spoken to anyone, then he should perform two rak’ahs.