What is the meaning of the Hadith: "The Messenger of Allah, may Allah bless him and grant him peace, sent a collector of zakat. A man came to him with a full-grown sheep, but he did not accept it, saying: 'Bring me a weaned sheep (mu'tat),' " and what is its grading?

It is narrated that Sa'ar bin Disam was sent for, to take the sadaqah (charity) of his sheep. He asked about the type of livestock required. The two messengers replied that they were the messengers of the Messenger of Allah (peace be upon him), and that he had forbidden them from taking the shafi' (a pregnant ewe or one with its offspring), and that they should take the anaq (a female kid, a goat) that is jadhaah (four months old) or thaniyyah (one year old). So, he gave them an anaq that was mutat (one that had not conceived due to its fatness). The chain of narration of this hadith is weak because Muslim bin Thafnah is unknown.