The Prophet ﷺ washed his private area three times.
حدثنا وكيع حدثنا شريك عن جابر عن زيد العمي عن أبي الصديق
أن النبي ﷺ غسل مقعدته ثلاثا
No references are available.
Its isnad is daif, because of Jabir Jafi and Zayd bin Hawari Ammi, both of whom are graded weak. Busiri said the same in his commentary on Zawaid bin Majah 1/127, no. 356, in the chapter on purification.