Musannaf Ibn Abi Shayba 36:84

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