Musannaf Ibn Abi Shayba 13:2572

Abu Bakr narrated to us, he said: Some of the sheikhs narrated to us, from Qays, from al-Ala’ ibn al-Musayyab, from Hammad, from Ibrahim, who said: There is no harm in a camel being sold for a camel with ten dirhams between them, if the animal is delivered immediately and the dirhams are present. And he disliked it if the dirhams were delivered immediately and the animal was delayed.