Jami` at-Tirmidhi Hadith 621

"The Messenger of Allah had a letter written about charity, but he had not dispatched it to his governors until he died; he kept it with him along with his sword. When he died, Abu Bakr implemented it until he died, as did Umar until he died. In it was: 'A sheep (is due) on five camels, two sheeps on ten, three sheeps on fifteen, four sheeps for twenty, a Bint Makhad on twenty-five to thirty-five. When it is more than that, then a Bint Labun, (is due, till the number of the camels reaches) forty-five. When it is more than that, then a Hiqqah until sixty. When it is more than that, then a Jadhah until seventy-five. When it is more than one hundred and twenty, then a Hiqqah on every fifty, and a Bint Labun on every forty. For sheep; one sheep (is due) for every forty sheeps until one hundred and twenty. When it is more than that, then two sheeps until two hundred. When it is more than that, then three sheeps until three hundred sheep. When it is more than three hundred sheep, then a sheep on every hundred sheep. Then there is nothing until it reaches four hundred. There is no combining the (property of) individuals nor separating the collective (property) fearing Sadaqah. And fr whatever is mixed together that two own, then they are to refer to the total. Neither an old or defective (animal) may be taken for charity."