It is narrated from Yazid bin Abdullah bin Qusayt (may Allah have mercy on him) that he saw Sa'id bin al-Musayyib (may Allah have mercy on him) get a nosebleed during the prayer, so he came to the room of the Mother of the Believers Umm Salamah (may Allah be pleased with her). A vessel of water was brought, he performed ablution, then he went back and continued on the same prayer.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3389