Musannaf Ibn Abi Shayba 27:711

'Abd al-Rahim ibn Sulayman narrated to us, from Isra'il, from Simak ibn Harb, from Sa'id ibn Jubayr, from Ibn 'Abbas regarding: "You are the best nation produced [as an example] for mankind," he said: "Those who migrated with Muhammad, may Allah bless him and grant him peace, to Medina."