Musannaf Ibn Abi Shayba 3:3525

Hushaym narrated to us, he said: Ibn Abi Layla informed us, from Nafi’, from Ibn Umar, who said: Whoever experiences a nosebleed during his prayer, let him depart and perform ablution. If he has not spoken, he shall continue from where he left off in his prayer. If he has spoken, he shall restart the prayer.