Ibn Jurayj (may Allah have mercy on him) said: I asked Ata' (may Allah have mercy on him): Is the diyah in animals or in gold? He replied: The diyah was camels only, but when the time of Sayyiduna Umar (may Allah be pleased with him) came, he set a value of 120 for each camel. Now if a villager pays 100 camels and does not give gold, this is according to the original rule.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الديات / 16169