John Calvin Commentary Genesis 14:17

"And the king of Sodom went out to meet him, after his return from the slaughter of Chedorlaomer and the kings that were with him, at the vale of Shaveh (the same is the King`s Vale)." — Genesis 14:17 (ASV)

And the king of Sodom went out. Although the king of Sodom knew that Abram had taken up arms only on account of his nephew, yet he went to meet him with due honor, in order to show his gratitude. For it is a natural duty to acknowledge benefits conferred upon us, even when not intentionally rendered, but only from unexpected circumstances and occasions, or (as we say) by accident.

Moreover, the whole affair yields greater glory to God, because Abram's victory was celebrated in this manner. He also notes the place where the king of Sodom met Abram, namely, “the king’s dale,” which I think was so called after a particular king, rather than because those kings met there for their pleasure.