Sunan an-Nasai Book 23, Hadith 2457

أَخْبَرَنَا هَنَّادُ بْنُ السَّرِيِّ، عَنْ هُشَيْمٍ، عَنْ هِلاَلِ بْنِ خَبَّابٍ، عَنْ مَيْسَرَةَ أَبِي صَالِحٍ، عَنْ سُوَيْدِ بْنِ غَفَلَةَ، قَالَ أَتَانَا مُصَدِّقُ النَّبِيِّ صلى الله عليه وسلم فَأَتَيْتُهُ فَجَلَسْتُ إِلَيْهِ فَسَمِعْتُهُ يَقُولُ ‏"‏ إِنَّ فِي عَهْدِي أَنْ لاَ نَأْخُذَ رَاضِعَ لَبَنٍ وَلاَ نَجْمَعَ بَيْنَ مُتَفَرِّقٍ وَلاَ نُفَرِّقَ بَيْنَ مُجْتَمِعٍ ‏"‏ ‏.‏ فَأَتَاهُ رَجُلٌ بِنَاقَةٍ كَوْمَاءَ فَقَالَ ‏"‏ خُذْهَا ‏"‏ ‏.‏ فَأَبَى

It was narrated that Suwaid bin Ghafalah said:"The Zakah collector of the prophet came to us, and I went to him, sat with him, and heard him say: In my contract it says that we should not take any sucking young, nor combine what is separate, nor separate what is combined.' A man brought a she-camel with a big hump to him and said: 'Take it, but he refused." (Daif)