Muwatta Malik, Book 2, Hadith 49 (USC-MSA) ⓘ
Yahya related to me from Malik from Nafi that Abdullah ibn Abbas used to have nose-bleeds and would leave to wash off the blood. He would then return and complete his prayer.
وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ عَبْدَ اللَّهِ بْنَ عَبَّاسٍ، كَانَ يَرْعُفُ فَيَخْرُجُ فَيَغْسِلُ الدَّمَ عَنْهُ ثُمَّ يَرْجِعُ فَيَبْنِي عَلَى مَا قَدْ صَلَّى .
also referenced under: Book 2, Hadith 79 (In-Book)