Musnad Ahmad 1:71

Abu Kamil narrated to us, Hammad ibn Salamah narrated to us, he said: I took this book from Thumamah ibn Abdullah ibn Anas, from Anas ibn Malik: That Abu Bakr wrote for them: These are the obligatory alms (zakat) which the Messenger of Allah (peace and blessings of Allah be upon him) obligated upon the Muslims, which Allah the Almighty commanded His Messenger (peace and blessings of Allah be upon him) with. Whoever among the Muslims is asked for them according to their proper manner, let him give them, and whoever is asked for more than that, let him not give it: "Regarding what is less than twenty-five camels: for every five camels, there is one sheep. When they reach twenty-five, there is a *bint makhad* (a one-year-old female camel) up to thirty-five. If a *bint makhad* is not available, then a *ibn labun* (a two-year-old male camel) is accepted. When they reach thirty-six, there is a *bint labun* (a two-year-old female camel) up to forty-five. When they reach forty-six, there is a *hiqqah* (a three-year-old female camel) that is ready for the stallion, up to sixty. When they reach sixty-one, there is a *jadha'ah* (a four-year-old female camel) up to seventy-five. When they reach seventy-six, there are two *bint labun* up to ninety. When they reach ninety-one, there are two *hiqqah* ready for the stallion up to one hundred and twenty. If they exceed one hundred and twenty, then for every forty there is a *bint labun*, and for every fifty there is a *hiqqah*." When the ages of the camels differ regarding the obligatory alms: whoever is liable for a *jadha'ah* as alms but does not have a *jadha'ah* and has a *hiqqah*, it shall be accepted from him, and he shall add two sheep with it if they are easy for him, or twenty dirhams. Whoever is liable for a *hiqqah* as alms but has only a *jadha'ah*, it shall be accepted from him, and the alms-collector shall give him twenty dirhams or two sheep. Whoever is liable for a *hiqqah* as alms but does not have one and has a *bint labun*, it shall be accepted from him, and he shall add two sheep with it if they are easy for him, or twenty dirhams. Whoever is liable for a *bint labun* as alms but has only a *hiqqah*, it shall be accepted from him, and the alms-collector shall give him twenty dirhams or two sheep. Whoever is liable for a *bint labun* as alms but does not have a *bint labun* and has a *bint makhad*, it shall be accepted from him, and he shall add two sheep with it if they are easy for him, or twenty dirhams. Whoever is liable for a *bint makhad* as alms but has only a *ibn labun* (male), it shall be accepted from him, and there is nothing else with it. Whoever has only four camels, there is nothing due upon them unless their owner wishes [to give voluntarily]. Regarding the alms of sheep, in their pastured livestock: when there are forty, there is one sheep up to one hundred and twenty. If they increase, there are two sheep up to two hundred. If they increase by one, there are three sheep up to three hundred. If they increase further, then for every hundred there is one sheep. An aged sheep, one with a defect, or a ram shall not be taken for alms unless the alms-giver wishes. Neither shall those who are separate be gathered together, nor shall those who are gathered be separated for fear of the alms. Whatever is held by two partners, they shall settle between themselves equally. If a man's pastured livestock is one sheep short of forty, there is nothing due upon them unless their owner wishes. Regarding silver (*riqqah*), one-quarter of a tenth is due. If the wealth is only one hundred and ninety dirhams, there is nothing due upon it unless its owner wishes.