Suwayd bin Ghafalah said: The zakah collector of the Messenger of Allah (peace and blessings be upon him) came to us. I took hold of his hand and he took hold of mine, and I read in his written covenant: "Separate holdings are not to be combined, nor combined holdings separated, for fear of (paying more) zakah." Then a man brought him a large she-camel, but he refused to take it. Then he brought another, inferior to it, and he refused to take that too. Then he said: Which earth would carry me and which sky would shade me if I came to the Messenger of Allah (peace and blessings be upon him) having taken the best of a Muslim's wealth?
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6444