Ayesha R.A. reported:
Rasulullah (ﷺ) and I bathed in one utensil, and the mubarak hair of Rasulullah (ﷺ) was longer than those that reached the ear lobes, and were less than those that reached the shoulders". (It means that they were not very long nor were they short, but of a medium length).
English reference: Book 3, Hadith 24
Arabic reference: Book 3, Hadith 25