Musnad Ahmad 31:387

Abu Sa’id narrated to us, Jahdam—meaning al-Yamami—narrated to us, Muhammad ibn Ibrahim narrated to us, from Muhammad ibn Zayd, from Shahr ibn Hawshab, from Abu Sa’id, who said: "The Messenger of Allah (peace and blessings of Allah be upon him) forbade the purchasing of what is in the bellies of livestock until they give birth, and [he forbade] what is in their udders except by measurement. And [he forbade] the purchasing of a slave while he is a runaway, and the purchasing of war spoils until they are divided, and the purchasing of charity [zakat] until it is collected, and the 'diver’s strike' [a form of gambling/uncertain transaction]."