Musannaf Ibn Abi Shaybah 21639 — A man who buys something

Sa'id bin al-Musayyib was asked about a man who bought a camel and then regretted the transaction, so he returns the camel and gives eight dirhams along with it: how is it to do so? Sa'id said: "There is no harm in it. Usury (riba) is only in what is measured or weighed, of what is eaten and drunk."