John Trapp on Psalms 103:11

Verſ. 11. For as the heaven is high above the earth] How high the third heaven is cannot be conjectured. But for the middlemoſt heaven (wherein the Sun, Moon, and Stars, are placed) how exceeding high it is may be gueſſed and gathered, in that the Stars (whereof thoſe of the firſt magnitude, are ſaid to be every one above a hundred and ſeven times as big again as the whole earth) do yet ſeem to us but as ſo many ſparks or ſpangles. See Prov. 25.3. Eph. 4.10.

So great is his mercy] The heavens are exceeding high above the earth, but Gods mercy to his is above the heavens, Pſal. 108.4. The original word Gabbar here uſed, is the ſame with that Gen. 7.20. uſed for the prevailing of the waters above the mountains.