Musnad Ahmad 941:2

Yahya ibn Ishaq and 'Affan narrated to us, they said: Wuhayb narrated to us, 'Abdullah ibn Tawus narrated to us, from his father, from Ibn 'Abbas, from Usamah ibn Zayd, that the Messenger of Allah (may Allah bless him and grant him peace) said: "There is no riba (usury) in that which is hand-to-hand (spot transaction)." He said: Meaning, riba is only in an-nasi'ah (deferred transactions).