It was narrated that Ghudaif bin Al-Harith said:
"I entered upon 'Aishah and asked her: 'Did the Messenger of Allah (ﷺ) perform Ghusl at the beginning of the night or at the end?' She said: 'Both. Sometimes he performed Ghusl at the beginning and sometimes at the end.' I said: 'Praise be to Allah who has made the matter flexible.'"
English reference: Vol. 1, Book 1, Hadith 224
Arabic reference: Book 1, Hadith 225