John Calvin Commentary Genesis 14:15

"And he divided himself against them by night, he and his servants, and smote them, and pursued them unto Hobah, which is on the left hand of Damascus." — Genesis 14:15 (ASV)

And he divided himself against them. Some explain these words to mean that Abram alone, with his household troops, rushed upon the enemy. Others suggest that he and his three allies divided their forces to strike greater terror into the enemy. A third group supposes the phrase to be a Hebraism, meaning a sudden attack into the midst of the enemy.

I prefer the second interpretation: namely, that he invaded the enemy from different sides and suddenly struck them with terror. The timing supports this view, because he attacked them by night.

And although examples of similar bravery occur in secular history, it should be attributed to Abram's faith that, with a small band, he dared to attack a numerous army elated with victory. But that he emerged victorious with little trouble, and fearlessly pursued those who far outnumbered him, we must attribute to the favor of God.