Isaiah 36:8

Now, therefore, give pledges - Margin, 'Hostages.' The Hebrew verb (ערב ‛ârab) means properly to mix or mingle; then, to exchange commodities by barter or traffic; then, to become surety for anyone, to exchange with him, to stand in his place; then, to pledge, to pledge one's life, or to give security of any kind. Here it is used in a spirit of taunting or derision, and is equivalent to what would be said among us, 'I will bet you, or I will lay a wager, that if we should give you only two thousand horses, you could not find men enough to ride them, or men that had knowledge of horsemanship enough to guide them.' There was much severity in this taunt. The Jews hoped to defend themselves. Yet here was an immense army coming up to lay siege against them. What hope had they of defense? So weak and feeble were they, that Rabshakeh said they could not furnish even two thousand horsemen to resist all the host of the Assyrians. There was also, doubtless, much truth in this taunt. It was not permitted by the law of Moses for the Jews to keep cavalry, nor for their kings to multiply horses. The reason of this may be seen in the notes at Isaiah 2:7. Though some of the kings, and especially Solomon, had disregarded this law of Moses, yet Hezekiah had endeavored to restore the observance of the law, and it is probable that he find no cavalry, and that the art of horsemanship was little known in Jerusalem. As the Assyrians prided themselves on their cavalry, they consequently looked with contempt on a people who were destitute of this means of defense.