(3) باب فِي تَخْفِيفِهِمَا
Narrated 'Abd Allah b. 'Abbas:
The Messenger of Allah (ﷺ) used to recite in both rak'ahs of the dawn prayer: "Say: We believe in Allah and in the revelation given to us" (3:84) . This is in the first rak'ah and in the second rak'ah (he recited): "We believe in Allah and bear witness that we submit ourself (to Him)." (3:52).
Reference: Sunan Abi Dawud 1259
In-book reference: Book 5, Hadith 10
English translation: Book 5, Hadith 1254