Sunan an-Nasa'i, Volume 1, Book 4, Hadith 424 (DarusSalam) ⓘ

It was narrated that 'Aishah said: "When the Messenger of Allah performed Ghusl from Janabah, he would call for something like a vessel used for milking a she-camel, then he would take (some water) in his hand and start with the right side of his head, then the left, then take (some water) in his hands and start pouring it on his head."

أَخْبَرَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، قَالَ حَدَّثَنَا الضَّحَّاكُ بْنُ مَخْلَدٍ، عَنْ حَنْظَلَةَ بْنِ أَبِي سُفْيَانَ، عَنِ الْقَاسِمِ، عَنْ عَائِشَةَ، قَالَتْ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِذَا اغْتَسَلَ مِنَ الْجَنَابَةِ دَعَا بِشَىْءٍ نَحْوِ الْحِلاَبِ فَأَخَذَ بِكَفِّهِ بَدَأَ بِشِقِّ رَأْسِهِ الأَيْمَنِ ثُمَّ الأَيْسَرِ ثُمَّ أَخَذَ بِكَفَّيْهِ فَقَالَ بِهِمَا عَلَى رَأْسِهِ ‏.‏