Genesis 14:15

And he divided them at night in the way; a part were to engage with the kings, and a part were hidden to smite the firstborn of Egypt. And he arose, he and his servants, and smote them, and pursued them which remained of them unto (the place) of the memorial of sin which was to be in Dan, from the north of Darmesek.

AND HE DIVIDED HIMSELF, BY NIGHT. Rashi wrote: “In accordance with the plain sense of the verse it means [that they divided into groups] as is the manner of those who pursue their enemies when they flee in different directions. By night means that even after it became dark, they did not cease pursuing them.”
The correct interpretation is that he pursued the enemies to Dan during the daytime with his entire army. When it became dark and he was not able to see by which road they fled, he divided his people and servants into two or three groups, taking one part with him, and they pursued them on all roads, smiting them as far as Hobah, which is on the left hand of Damascus. Then he returned from pursuing them. The order of the words [in the verse are thus interpreted as follows]: “And he divided himself, he and his servants, by night.”

AND HE PURSUED THEM UNTO HOBAH, WHICH IS ON THE LEFT HAND OF DAMASCUS. It is known that there is a great distance from the oaks of Mamre in Hebron in the land of Judah, to Damascus, which is outside the Land. If so, he pursued them for many days until he forced them to leave the land for they were returning to Babylon, their country. Or possibly there occurred here a great miracle, just as our Rabbis expounded from the verse, The way with his foot he treadeth not.

ויחלק עליהם לילה, he divided his forces all around them to make them believe that they were being attacked by large forces from several fronts. We have been told about a similar situation in Kings II 7,6 when the Aramites fled headlong after hearing noises that convinced them that they were being attacked by large forces.

לילה, this was also part of the subterfuge, preventing the kings from realising that they were facing insignificant numbers of opponents. In Samuel II 17,1 this was the advice to Avshalom by Achitofel when he advised to pursue David at night.

ויכם, the defeat caused them to flee.

וירדפם, the beginning of all pursuits is putting people to flight.

ויחלק עליהם לילה, “when it was midnight, they attacked them. The word עליהם refers to the armies of the four kings, not as if it was midnight only for Avram and his men. As to the unusual expression עליהם, instead of the normative expression ויהי בחצי הלילה, “it was at midnight,” this tells us that until midnight on that night the four kings had felt absolutely safe and secure. Starting at that moment, they began to flee for their lives as soon as they found themselves under surprise attack by Avram and his men. He smote them as soon as he caught up with them, and those whom he did not catch continued fleeing all the way to Chovah, close to Damascus. The defeat was especially great, seeing that the fleeing armies left behind all their belongings, aiming only to save their lives. After having chased them such a great distance, Avram turned back and restored all the loot these kings had captured to their rightful owners.

ויכם וירדפם, “he smote them and put them to flight.” Midrash Tanchuma asks: “who ever heard of soldiers pursuing dead people? How are we to understand this sequence in the verse?” He therefore understands our verse as meaning that Avraham and his men pursued the soldiers of that army, and G–d killed them.