Anas said that when Abu Bakr sent him to al-Bahrain he wrote him this letter

In the name of Allah, the Compassionate, the Merciful. This is the obligatory sadaqa which Allah's Messenger ﷺ imposed on the Muslims which Allah commanded him to impose. Those Muslims who are asked for the proper amount must give it, but those who are asked for more than that must not give it. For twenty-four camels or less, a sheep is to be given for every five. When they reach twenty-five to thirty-five, a she-camel in her second year is to be given. When they reach thirty-six to forty-five, a she-camel in her third year is to be given. When they reach forty-six to sixty, a she-camel in her fourth year which is ready to be covered by a stallion is to be given. When they reach sixty-one to seventy-five, a she-camel in her fifth year is to be given. When they reach seventy-six to ninety, two she-camels in their third year are to be given. When they reach ninety-one to a hundred and twenty, two she-camels in their fourth year which are ready to be covered by a stallion are to be given. When they exceed a hundred and twenty, a she-camel in her third year is to be given for every forty and a she-camel in her fourth year for every fifty. If anyone has only four camels, no sadaqa is payable on them unless their owner wishes, but when they reach five a sheep is payable on them. If anyone whose camels reach the number on which a she-camel in her fifth year is payable does not possess one but possesses one in her fourth year, that will be accepted from him along with two sheep if he can conveniently give them, or else twenty dirhams. If anyone whose camels reach the number on which a she-camel in her fourth year is payable does not possess one but possesses one in her fifth year, that will be accepted from him, and the collector must give him twenty dirhams or two sheep. If anyone whose camels reach the number on which a she-camel in her fourth year is payable possesses only one in her third year, that will be accepted from him along with two sheep or twenty dirhams. If any one whose camels reach the number on which a she-camel in her third year is payable possesses one in her fourth year, that will be accepted from him, and the collector must give him twenty dirhams or two sheep. If anyone whose camels reach the number on which a she-camel in her third year is payable does not possess one but possesses one in her second year, that will be accepted from him, and he must give along with it twenty dirhams or two sheep. If anyone whose camels reach the number on which a she-camel in her second year is payable does not possess one but possesses one in her third year, that will be accepted from him, and the collector must give him twenty dirhams or two sheep; but if he does not possess a she-camel in her second year as is required and possesses a male camel in its third year, that will be accepted from him and nothing extra is to be demanded along with it. Concerning the sadaqa on sheep which are pasturing, when they number from forty to a hundred and twenty, a sheep is to be given. On over a hundred and twenty up to two hundred two sheep are to be given. On over two hundred up to three hundred three sheep are to be given. If they exceed three hundred, a sheep is to be given for every hundred. If a man’s pasturing animals are one less than forty no sadaqa is due on them unless their owner wishes. An old sheep, one with a defect in the eye, or a male goat is not to be brought forth as sadaqa unless the collector is willing. Those which are in separate flocks are not to be brought together and those which are in one flock are not to be separated from fear of sadaqa. * Regarding what belongs to two partners, they can make claims for restitution from one another with equity. On dirhams a fortieth is payable, but if there are only a hundred and ninety nothing is payable unless their owner wishes. Bukhari transmitted it. * The principle is that there is to be no rearrangement either so that the collector may get more than he might, or the owner may give less than he might.