Sunan Abi Dawud Book 2, Hadith 358
Abdullah ibn Mas'ud said: Should I not pray for you the way the Messenger of Allah (ﷺ) prayed? So he prayed, raising his hands only once.
Abu Dawud said: This is a summarized version of a longer narration and it is not authentic with this wording.
The Messenger of Allah (ﷺ) taught us how to pray. He then uttered the takbir (Allah is most great) and raised his hands; when he bowed, he joined his hands and placed them between his knees. When this (report) reached Sa'd, he said: My brother said truly. We used to do this; then we were later on commanded to do this, that is, to place the hands on the knees.
He raised his hands once in the beginning. Some narrated: (raised his hands) once only.