We used to take the oath of allegiance to the Prophet (ﷺ) to hear and obey, and he would tell: In What I am able.
Sunan Abi Dawud Book 20, Hadith 13
← Previous Hadith 'Umar said: I shall not appoint a successor, for the Messenger of Allah (ﷺ) did not appoint a successor. If I appoint a successor (I can do so), for Abu Bakr had appointed a successor. He Ibn 'Umar) said: I swear by Allah, he did not mention (anyone) but the Messenger of Allah (ﷺ) and Abu Bakr. So I learnt he would not equate anyone with the Messenger of Allah (ﷺ), for he did not appoint any successor.

Sunan Abi Dawud Book 20, Hadith 12 Next Hadith → The Messenger of Allah (ﷺ) never touched the hand of woman, but he received the oath of allegiance from her. When he received the oath of allegiance from her, she gave it to him, and he said: Go, I have received your oath of allegiance.

Sunan Abi Dawud Book 20, Hadith 14