Sunan Ibn Majah, Volume 2, Book 5, Hadith 1315 (DarusSalam) ⓘ
It was narrated that Ibn ‘Abbas said: “The Messenger of Allah used to have a bath on the day of Fitr and the day of Adha.”
حَدَّثَنَا جُبَارَةُ بْنُ الْمُغَلِّسِ، حَدَّثَنَا حَجَّاجُ بْنُ تَمِيمٍ، عَنْ مَيْمُونِ بْنِ مِهْرَانَ، عَنِ ابْنِ عَبَّاسٍ، قَالَ كَانَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ يَغْتَسِلُ يَوْمَ الْفِطْرِ وَيَوْمَ الأَضْحَى .
also referenced under: Hadith 1315 (Reference) & Book 5, Hadith 1376 (In-Book)