John Gill Commentary Isaiah 55:9

"For as the heavens are higher than the earth, so are my ways higher than your ways, and my thoughts than your thoughts." — Isaiah 55:9 (ASV)

For as the heavens, are higher than the earth
Than which there cannot be conceived a greater distance: so are my ways higher than your ways, and my thoughts than your
thoughts ;
which may denote the heavenliness of the ways and thoughts of God, the eternity and unsearchableness of them, and their excellency and preciousness; as well as the very great distance between his ways and thoughts and men's which this is designed to illustrate.