Muwatta Malik, Book 10, Hadith 2 (USC-MSA)

Yahya related to me from Malik from Nafi that Abdullah ibn Umar used to do ghusl on the day of Fitr before going to the place of prayer.

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، كَانَ يَغْتَسِلُ يَوْمَ الْفِطْرِ قَبْلَ أَنْ يَغْدُوَ إِلَى الْمُصَلَّى ‏.‏

sunnah.com

also referenced under: Book 10, Hadith 432 (In-Book)