The Book of Prayers (Kitab Al-Salat)
Muslim :: Book 4 : Hadith 1577
Ibn 'Abbas reported that the Messenger of Allah (may peace be upon him) used to recite in the two (supererogatory) rak'ahs of the dawn prayer:" Say: We believed in Allah and what was revealed to us" and that which is found in Surah Al-i-'lmran:" Come to that word (creed) which is common between you and us" (iii. 64).