Charles Ellicott Commentary 1 Chronicles 19:18

"And the Syrians fled before Israel; and David slew of the Syrians [the men of] seven thousand chariots, and forty thousand footmen, and killed Shophach the captain of the host." — 1 Chronicles 19:18 (ASV)

Seven thousand men who fought in chariots, and forty thousand footmen. —Hebrew, seven thousand chariotry (rèkeb) , etc. Samuel reads, “seven hundred chariots, and forty thousand horsemen.” Such deviations seem to indicate independent sources. We can hardly choose between the two accounts; but “horsemen” may be more correct than “footmen.” (See 1 Chronicles 18:4–5.)

And killed Shophach ... —Abridged statement. (Compare to 2 Samuel 10:18.)