Musannaf Ibn Abi Shayba 13:1394

Abu Bakr narrated to us, he said: Ibn Abi Za’idah narrated to us, from Muhammad ibn Ishaq, who said: I asked Abu Bakr ibn Muhammad ibn ‘Amr ibn Hazm about the *a’tan* (watering places for camels). He said: As for the people of the Jahiliyyah, it was fifty cubits for its side, so there would be one hundred between the two wells. When Islam came, they saw that less than that was sufficient, so they made for each well twenty-five cubits, [making] fifty cubits for its side.