Musnad Ahmad 25:605

Husayn and Abu Nu'aym narrated to us, they said: Isra'il narrated to us, from Simak, from Sa'id ibn Jubayr, from Ibn Abbas, regarding His saying, the Almighty and Majestic: "You are the best nation produced [as an example] for mankind: you enjoin what is right and forbid what is wrong" [Al 'Imran: 110]. He said: "They are those who migrated with Muhammad, may Allah bless him and grant him peace, to Medina." Abu Nu'aym said: "With the Prophet, may Allah bless him and grant him peace."