Genesis 14:23

The patriarch's contempt for material wealth was intense. Why is it with an oath that he rejects the offer in the words "I will raise my hand to swear before God the most high, who created heaven and earth"? He wants to give the king of Sodom two lessons. First, he is above the gifts offered by him; and this gives evidence of great wisdom. He is ready to prove an instructor for him in reverence, as if to teach him in so many words: I am calling to witness the Creator of all that I will take nothing of yours, so that you may come to know the God over all and not regard as gods the things shaped by human hands. This One in fact is the maker of heaven and earth, who indeed determined the course of this war and was the cause of victory. So don't expect me to be ready to take anything you've offered me. It was not, you see, for a reward that I wreaked vengeance. Instead, in the first instance it was out of love for my nephew, and then from the very nature of a good man that I should wrest from the clutches of barbarians people wrongfully abducted.

It is characteristic of the perfect mind not to take for itself any earthly thing, anything prone to bodily seduction. This is why Abraham says, "I will take nothing of what is yours." He avoids intemperance like the plague. He flees from sensual bodily temptations as from filth. He rejects worldly pleasures to seek those that are above the world. This is what it means to raise one's hands to the Lord. The hand that does good is the virtue of the soul. He puts forth his hand not to the fruit of the earthly tree but to the Lord, "who," Scripture says, "made heaven and earth," that is to say, both intelligible and visible substance. In fact, the invisible ousia, or substance, is heaven, while the earth is the visible and sensible substance. The passage then means that Abraham raises the virtue of his mind to heavenly things. From that intelligible substance he might reach the heights of the contemplative life, looking not to the things that are seen but to those that are not seen; not to earthly things, not to bodily things; not to things present but to things that are immaterial, eternal, heavenly. But from that other substance, the visible, he extracts the benefit of a discipline related to the practical order and to civil life.

He would not take even a chance item, even something worthless or anything thought beneath contempt, even the shoelace at the tip of the shoe, where it comes to a point. Then he states the reason for his refusal. It is "in case you were to say, 'I gave Abram his wealth.' I have on my side the supplier of countless goods; I enjoy much favor from on high. I have no need of wealth from you. I don't want human resources. I am content with the regard God pays me. I know the generosity of his gifts toward me. Having yielded to Lot worthless scraps, I have been granted great promises beyond telling. Now by not accepting wealth from you I earn for myself greater wealth and enjoy further grace from him." This in my opinion … was the reason why he took the oath in the words "I will raise my hand to swear before God the most high"; namely, that the king should not think that he was simply putting up a pretense about what was likely to happen but should rather be quite clear about his not taking the least trinket from him. He was honoring that command given by Christ to the disciples: "Freely you have received, freely give." In other words, he is saying, Surely I have contributed nothing to the course of the war other than consent and encouragement, whereas the victory and the spoils and everything else has been God's work in his invisible might.