Sunan Ibn Majah, Chapter: The Chapters Regarding Zakat

"The Zakah collector of the Prophet (saw) came to us, and I took him by the hand and read in his order: 'Do not gather separate herds and do not separate herd for fear of Sadaqah'. A man brought him a huge, fat she-camel, but he refused to accept it. So he brought him another of lower quality and he accepted it. He said: 'What land would shelter me, if I came to the Messenger of Allah (saw) having taken the nest of a Muslim man's camels?' " Hasan