John Gill

Whose arrows are sharp, and all their bows bent,.... Ready to shoot their arrows upon any occasion; and which being sharp, penetrated deep, and were deadly. This includes all kind of warlike instruments, with which they should come furnished, and ready prepared to do execution: their horses' hoofs shall be counted like flint; by those who rode upon them; who knowing how strong and firm they were, and that they were not worn out, nor hurt by the length of the way they came, would not spare to make haste upon them: and their wheels like a whirlwind; that is, the wheels of their chariots, they used in battle, as Aben Ezra, Jarchi, and Kimchi, interpret it; and so the Septuagint and Arabic versions render it: this metaphor denotes both the swiftness with which they should come, and the noise and rattling they should make, and the power and force in bearing down all before them. The Targum is, "and his wheels swift as a tempest.''