Albert Barnes Commentary Proverbs 18:11

"The rich man`s wealth is his strong city, And as a high wall in his own imagination." — Proverbs 18:11 (ASV)

What the name of the Lord is to the righteous (Proverbs 18:10), that wealth is to the rich. He flees to it for refuge as to a strong city; but it is so only in his own conceit or imagination.

High - In the Hebrew the same word as safe (Proverbs 18:10), and manifestly used in reference to it.