From Sahih Muslim (Hadith 1761):
Anas b. Sirin reported:I asked Ibn 'Umar to tell me about the practice of the Prophet (ﷺ) in regard to two rak'ahs before the dawn prayer: Should I make lengthy recitation in them? He said: The Messenger of Allah (ﷺ) used to observe, the night prayer in pairs and then made the number odd by observing one rak'ah. I said: I am not asking you about it. He said: You are a bulky man, will you not show me the patience to narrate to you the hadith completely? The Messenger of Allah (ﷺ) used to observe the night prayer in pairs and then made the number odd by observing one rak'ah, and then he observed two rak'ahs before dawn quite close to the call for prayer (Khalaf said:" Did you see [yourself the Prophet observing] the two rak'ahs before the dawn?" and he made no mention of prayer
Reference: Muslim 1761