"I asked 'Aishah: 'How did the Messenger of Allah (ﷺ) sleep while he was Junub? Did he perform Ghusl before sleeping or sleep before performing Ghusl?' She said: 'He did both. Sometimes he would perform Ghusl then sleep, and sometimes he would perform Wudu' then sleep.'"
Sunan an-Nasa'i Book 4, Hadith 9
← Previous Hadith "The Prophet (ﷺ) used to say: 'Allahumma tahhirni bith-thalji wal-barad wal-ma' al-barid, Allahumma tahhirni min adh-dhunub kama yutahhar ath-thawb al-abyad min ad-danas (O Allah, purify me with snow and hail and cold water, O Allah, purify me of sin as a white garment is cleansed of dirt)."

Sunan an-Nasa'i Book 4, Hadith 8 Next Hadith → "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.'"

Sunan an-Nasa'i Book 4, Hadith 10