Musannaf Ibn Abi Shayba 18:149

Abu Bakr narrated to us, he said: Muhammad bin Bakr narrated to us, from Ibn Jurayj, he said: Abd al-Karim bin Abi al-Mukhariq informed me that it reached him from some of the companions of the Prophet, may God bless him and grant him peace, regarding the eyebrow, that if one removes its hair, there is in its entirety a quarter [of the blood money], and regarding what is gone of it, then it is by calculation.