Bishr bin Asim narrates from his father that Sayyiduna Umar (may Allah be pleased with him) appointed his father, Sufyan bin Abdullah (may Allah be pleased with him), as governor over Ta'if and its surrounding districts, and he went out to collect zakah. He counted their young lambs against them but did not take them from them, so they said: If you count the young lambs against us, then take them from us. So he held back until he met Sayyiduna Umar (may Allah be pleased with him) and said: Know that they claim that we wrong them by counting the young lambs against them while not taking them from them. Sayyiduna Umar (may Allah be pleased with him) said to him: Count the young lambs against them, even the newborn that the shepherd brings carrying it on his hand, and tell them: I do not take from you the ewe that has just given birth, nor the pregnant one, nor the milking one, nor the sheep fattened for eating, nor the stud of the flock; and take the jadha'ah kid (less than a year old) and the thaniyyah, for that is fairness between the young of the wealth and its best.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7301