For he bringeth down Hebrew, he hath brought down, or, as it may be rendered, he will bring down, them that dwell on high He speaks not so much of height of place, as of dignity and power, in which sense also he mentions the lofty city in the next clause; which may be understood, either of proud Babylon, or of all the strong and stately cities of God's enemies. The foot shall tread it down God will bring it under the feet of his poor, weak, and despised people. The meaning is, you have good reason for trusting in God, for he can and does raise up some and throw down others, according to his own good pleasure.
Related Commentaries of Isaiah 26:5
Isaiah 26:5-6
5 For he bringeth down them that dwell on high; the lofty city, he layeth it low; he layeth it low, even to the ground; he bringeth it even to the dust.
6 The foot shall tread it down, even the feet of the poor, and the steps of the needy.