Charles Ellicott Commentary 2 Kings 18:23

"Now therefore, I pray thee, give pledges to my master the king of Assyria, and I will give thee two thousand horses, if thou be able on thy part to set riders upon them." — 2 Kings 18:23 (ASV)

Give pledges to. —Rather, make a compact with... So the Syriac; literally, mingle with... have dealings with (Psalms 106:35). Gesenius explains: join battle with; literally, mingle yourselves with; Septuagint, μίχθητε δὴ. Mr. Cheyne prefers lay a wager with...

The Rabshakeh sneers at Hezekiah’s lack of cavalry, a military branch in which the Assyrians were preeminently strong. He further hints that even if horses were supplied to him in numbers sufficient to constitute an ordinary troop, Hezekiah would not be able to muster an equivalent number of trained riders.