Albert Barnes 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 — You who proposed an alliance with Egypt.

For we will flee upon horses — The word ‘flee’ (נוּס nûc) usually signifies to flee before or from any person or thing. But here it seems to mean making a rapid motion in general, and not that they expected to flee from their enemy, as this does not seem to have been their expectation. The idea appears to be that by their alliance with Egypt they would secure the means of rapid motion, whatever the necessity or occasion for it, whether against or from an enemy. The sense is, ‘we will by this alliance secure the assistance of cavalry;’ and, doubtless, the design was to employ it in the attack and discomfiture of their foes.

It will be recalled that Moses (Deuteronomy 17:16) strictly forbade the future monarch of the Jews to multiply horses to himself, to cause the people to return to Egypt, and that consequently the employment of cavalry was against the laws of the nation. For the reasons for this prohibition, see the note at Isaiah 2:7.

The attempt, therefore, in the time of Hezekiah to call in the aid of the cavalry of Egypt, was a violation of both the letter and the spirit of the Jewish institutions (Hosea 14:4).

Therefore you shall flee — You shall fly before your enemies; you shall be defeated and scattered.

We will ride upon the swift — That is, upon fleet horses or coursers. Arabia was celebrated, and is still, for producing fleet coursers, and the same was formerly true of Egypt (see the note at Isaiah 2:7).