Muwatta Malik, Book 2, Hadith 48 (USC-MSA)

Yahya related to me from Malik from Nafi that Abdullah ibn Umar would leave and do wudu if he had a nose-bleed and then return and complete his prayer without saying anything.

حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ نَافِعٍ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، كَانَ إِذَا رَعَفَ انْصَرَفَ فَتَوَضَّأَ ثُمَّ رَجَعَ فَبَنَى وَلَمْ يَتَكَلَّمْ ‏.‏

sunnah.com

also referenced under: Book 2, Hadith 78 (In-Book)