Musannaf Ibn Abi Shayba 18:400

Abu Bakr narrated to us, he said: al-Dahhak ibn Makhlad narrated to us, from Ibn Jurayj, from ‘Amr ibn Shu‘ayb, that ‘Umar ibn al-Khattab ruled regarding a fingernail, when it becomes inflamed and spoils, that [the compensation is] a young she-camel.