John Gill Commentary Deuteronomy 4:39

"Know therefore this day, and lay it to thy heart, that Jehovah he is God in heaven above and upon the earth beneath; there is none else." — Deuteronomy 4:39 (ASV)

Know therefore this day, and consider it in your heart
Own and acknowledge it now with your mouth, and lay it up and consider it in your heart hereafter, as a truth of the greatest importance to be professed and held fast, and to be thought of and meditated upon continually, and never to be forgotten:

that the Lord he is God in heaven above ,
and upon the earth beneath; that he has made both, and is the possessor and Lord of them, and does what he pleases with them; that the one is his throne, his dwelling place, and the other his footstool; and that the inhabitants of both are his creatures, and under his authority and command, and he can dispose of them as he pleases:

[there is] none else ;
no God in heaven or in earth beside him.