Rashi on Genesis 14:22/רש"י על בראשית י״ד:כ״ב

1הרמתי ידי I HAVE LIFTED UP MY HAND — An expression signifying an oath: I lift up my hand to the Most High God (not, I have lifted up). Similarly, (Genesis 22:16) בי נשבעתי which means “By myself do I swear” and similarly, (Genesis 23:13) נתתי כסף השדה קח ממני which means “I give the price of the field, take it from me”.)