Musannaf Ibn Abi Shayba 18:20

Abu Bakr narrated to us, he said: Muhammad ibn Bakr narrated to us, from Ibn Jurayj, from Ibn Tawus, he said: My father said: They are given from whichever category it may be, according to the value of the camels on that day, whether it was high or whether it was low, then it is its value.