Chapter 43: The Book of ad-Dahaya (Sacrifices)
It was narrated that 'Asim bin Kulaib said: "I heard my father narrating from a man who said: 'We were with the Messenger of Allah two days before Al-Adha and we started to offer two Jadh ahs for one Thaniiyah, Then the Messenger of Allah said: 'A Jadh' ah is sufficient for that for which a Thaniyah is sufficient."
Sunan an-Nasa'i 4384