John Gill Commentary Isaiah 30:16

"but ye said, No, for we will flee upon horses; therefore shall ye flee: and, We will ride upon the swift; therefore shall they that pursue you be swift." — Isaiah 30:16 (ASV)

But you said, No, for we will flee upon horses
Hither and thither to get help and assistance; go down to Egypt for it on them, or thither for them, as some render it; and then face the enemy, and, if we cannot conquer him, will flee from him, and so provide for our safety; this is man's way of salvation, as opposed to God's way; see (Hosea 1:7) (14:3) or this may design their fleeing on horses and camels with their riches into Egypt, both for the security of them and their persons, (Isaiah 30:6) :

therefore shall you flee ;
on horses from the enemy, and be pursued and taken by him; this was fulfilled long after, when the city was taken by the Chaldeans; see (2 Kings 25:4) :

and, We will ride upon the swift ;
horses or camels, to the swiftness of which they trusted, and doubted not to get off safe, but would find themselves mistaken:

therefore shall they that pursue you be swift ;
yea, swifter than the horses and camels they rode on, and overtake them, and either put them to death, or carry them captive. The Chaldeans are represented as very swift, (Jeremiah 4:13) (Habakkuk 1:8) .