Ibn 'Umar reported that Hafsa, the Mother of the Believers, informed him that when the Mu'adhdhin became silent after calling (people) to the dawn prayer, the Messenger of Allah (ﷺ) commenced the dawn (prayer) when it dawned by observing two short rak'ahs before the commencement of the (Fard) prayer

This hadith has been transmitted by Nafi' with the same chain of narrators

Hafsa reported that when it was dawn, the Messenger of Allah (ﷺ) did not observe (any other prayers) but two short rak'ahs

A hadith like this has been narrated by Shu'ba with the same chain of transmitters

Hafsa reported:When the dawn appeared, the Messenger of Allah (ﷺ) observed two rak'ahs (of Sunnah prayers)