The hair of the Messenger of Allah ﷺ reached halfway down his ears.
حدثنا مسدد حدثنا إسمعيل أخبرنا حميد
كان شعر رسول الله ﷺ إلى أنصاف أذنيه
No references are available.
Muslim narrated it in Sahih Muslim, Book of Virtues, Chapter on the Description of the Hair of the Prophet, no. 2338, from the hadith of Ismail bin Ulaya through this route.