Sunan Ibn Majah: Book 8, Hadith 18

Anas bin Malik narrated that: Abu Bakr Siddiq wrote to him: “In the name of Allah, the Most Gracious, the Most Merciful. This is the obligation of Sadaqah which the Messenger of Allah enjoined upon the Muslims, as Allah commanded the Messenger of Allah. The ages of camels to be given (in Zakat) may be made up in sheep. So if a man has camels on which the Sadaqah is a Jadha’ah (a four-year-old she-camel) and he does not have a Jadha’ah but he has a Hiqqah (a three year old she-camel), then the Hiqqah should be accepted from him, and two sheep should be given (in addition), if they are readily available, or twenty Dirham. If a man has camels on which the Sadaqah is a Hiqqah, and he only has a Bin Labun( a two-year-old she-camel), then the Bint Labun should be accepted from him, along with two sheep or twenty Dirhams.If a man has camels on which the sadaqah is a Bint Labun, and he does not have one, but he has a Hiqqah, then it should be accepted from him, and the Zakat collector should give him back twenty Dirham or two sheep. If a man has camels on which Sadaqah is a Bint Labun, and he does not have one, but he has a Bint Makhad(a one-year-old she-camel), then the Bint Makhad should be accepted from him, along with twenty Dirham or two sheep. If a man has camels on which the Sadaqah is a Bint Makhad, and he does not have one, but he has a Bint Labun, then the Bint Labun should be accepted from him, and the Zakat collector should give him back twenty Dirhams or two sheep. Whoever does not have a Bint Makhad, but he has a Bint Labun (a two-year-old male camel), then it should be accepted from him and nothing else should be given along with it.’ ”