Musannaf Ibn Abi Shayba 3:6253

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: I heard Sufyan saying regarding a man who entered [the prayer] with the Imam on Friday, then he had a nosebleed, so he went and performed ablution, then he came while the Imam had already finished the prayer, and the man did not speak. Sufyan said: He performs the prayer of the Imam, two rak'ahs. And Al-Hasan ibn Salih said: He performs four [rak'ahs], unless he had already performed one rak'ah with him.