Musannaf Ibn Abi Shayba 18:347

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Jarir ibn Hazim, from Humayd ibn Hilal, he said: In a document written by Marwan from Zayd ibn Thabit, he said: If you sever the glans of a man, then in it is half of the blood money.