Abu Bakr bin Muhammad bin Amr bin Hazm narrates from his father, from his grandfather, that the Prophet (peace and blessings be upon him) wrote a letter to the people of Yemen in which the obligatory duties, the Sunnahs and the diyahs were set out. Amr bin Hazm took that letter to them, and in it was also this: "For a life, the diyah is 100 camels."
Sayyiduna Umar, Ali, Abdullah and Zayd bin Thabit (may Allah be pleased with them) also say the same: the diyah for a life is 100 camels.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الديات / 16147