Sunan Abi Dawud Book 5, Hadith 46
The Prophet (ﷺ) said: Prayer by night and day should consist of pairs of rak'ahs.
I asked Jabir b. Samurah: Did you sit in the company of the Messenger of Allah (ﷺ) ? He replied: Yes, very often. He would not stand from the place he prayed the dawn prayer till the sunrise. When the sun rose, he would stand (to pray Duha).
The Prophet (ﷺ) said: Prayer is to be offered in two rak'ahs; and you should recite the tashahhud at the end of two rak'ahs, and express your distress and humility and raise your hands and say praying: O Allah, O Allah. He who does not do so does not offer a perfect prayer.
Abu Dawud was asked about offering prayer at night in two rak'ahs. He said: They may be two if you like and four if you like.