Isaiah 36:8

Now therefore give pledges, I pray thee, 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.

Give pledges - a taunting challenge. Only give the guarantee that you can supply as many as 2,000 riders, and I will give thee 2,000 horses. But seeing that you have not even this small number (note ), how can you stand against the hosts of Assyrian cavalry? The Jews tried to supply their weakness in this 'arm' from Egypt ().