For the Lord your God is a merciful God. He will not leave you or destroy you or forget the covenant with your fathers that he swore to them (Deuteronomy 4:31, ESV).
And Yahweh demonstrated His faithfulness in these ways, places, times, and manners:
The Lord your God who goes before you will himself fight for you, just as he did for you in Egypt before your eyes, and in the wilderness, where you have seen ho wthe Lord your God carried you, as a man carries his son, all the way that you went until you ame to this place (Deuteronomy 1:30-31, ESV).
For the Lord your God has blessed you in all the work of your hands. He knows your going through this great wilderness. These forty years the Lord your God has been with you. You have lacked nothing (Deut.2:7, ESV).
...the Lord your God...went before you in the way to seek you out a place to pitch your tents, in fire by night and in the cloud by day, to show you what way you should go (Deut.1:33, ESV).
For what great nation is there that has a god so near to it as the Lord our God is to us, whenever we call upon him? (Deut.4:7, ESV).
But the Lord has taken you and brought you out of the iron furnace, out of Egypt, to be a people of his own inheritance, as you are this day (Deut.4:20, ESV).
His faithfulness was proven to His people over and over again. Yet, when they went astray and worshiped false idols, it was because they did not keep His promises in the forefront of their minds. Forgetting God's covenants leads to false worship.
Did any people ever hear the voice of a god speaking out 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 tation, by trials, by signs, by wonders, and by war, and 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. (Deut.4:33-35, ESV)