Ramban, on Gen 14:22

“And he answered him: I lift up my hand to the Lord God the most high, the possessor of heaven and earth,”

“I HAVE LIFTED UP MINE HAND TO THE ETERNAL. This is an expression signifying an oath: “I lift up my hand to G-d Most High.”, the sense is that of the present tense: “I lift up my hand.” Similarly, the verse, By myself have I sworn, means “By Myself do I swear.” Thus the language of Rashi. I have found a similar text in the Sifre: 33. “We find in the case of all the righteous that they bring their inclination under oath in order not to do evil. In the case of Abraham, he says, I have lifted up mine hand to the Eternal.” It is thus similar to the verse, And he lifted up his right hand and his left hand unto heaven, and swore by Him that liveth forever. But Onkelos said, “I have lifted my hand in prayer before the Eternal.” The intent of Abraham’s words according to Onkelos is: “I have prayed to G-d, with my hands spread forth toward heaven, if I take anything that is thine.” That is to say, “G-d do so to me, and more also,, 2:23. if I take, etc.” The correct interpretation appears to me to be that Abraham said, “I have lifted my hand to G-d to make those things Sacred and Devoted to Him, were I to take from that which is thine.” Declaring things to be sacred to Him is called in Hebrew “lifting of a hand,” just as in the verses: Every one that did lift up a heave offering of silver and copper; and every man that offered a wave offering of gold unto the Eternal., Verse 22. This Abraham said because having given a tenth of it to the priest, he declared that whatever he takes from the king of Sodom would be a heave offering to G-d, from which he would derive no benefit. In Bereshith Rabbah it is similarly said, “Abraham made it a heave offering, even as it is said, And ye shall heave a heave offering of it for the Eternal.””

Imported from an open dataset — not yet checked against the printed edition.