Here is Moses’ amazing monotheistic appeal to the people of Israel at the edge of the Promised Land, after 40 years of wilderness wandering.
Ask now of the days that are past, which were before you, since the day that God created man on the earth, and ask from one end of heaven to the other, whether such a great thing as this has ever happened or was ever heard of.
Did any people ever hear the voice of a god speaking out of the midst of the fire, as you have heard, and still live?
Or has any god ever attempted to go and take a nation for himself from the midst of another nation, by trials, by signs, by wonders, and by war, by a mighty hand and an outstretched arm, and by great deeds of terror, all of which the LORD your God did for you in Egypt before your eyes?
To you it was shown, that you might know that the LORD is God; there is no other besides him.
Out of heaven he let you hear his voice, that he might discipline you. And on earth he let you see his great fire, and you heard his words out of the midst of the fire.
And because he loved your fathers and chose their offspring after them and brought you out of Egypt with his own presence, by his great power, driving out before you nations greater and mightier than yourselves, to bring you in, to give you their land for an inheritance, as it is this day, know therefore today, and lay it to your heart, that the LORD is God in heaven above and on the earth beneath; there is no other.
(Deuteronomy 4:32–39, paragraphing added)