Musannaf Ibn Abi Shaybah

It is narrated from Hazrat Abu Hurairah (may Allah be pleased with him) that the Holy Prophet (peace and blessings be upon him) said: The best camels are thirty. Among them, the strong and swift camels should be ridden. Those that are somewhat weak should be given on hire, and those that give plenty of milk should be given to someone as a gift. And when they come to their enclosure, their milk should be milked.