Deu 9:9-16 When I went up the mountain to receive the tablets of stone, the tablets of the covenant that the LORD made with you, I remained on the mountain forty days and forty nights. I neither ate bread nor drank water. And the LORD gave me the two tablets of stone written with the finger of God, and on them were all the words that the LORD had spoken with you on the mountain out of the midst of the fire on the day of the assembly. And at the end of forty days and forty nights the LORD gave me the two tablets of stone, the tablets of the covenant. Then the LORD said to me, ‘Arise, go down quickly from here, for your people whom you have brought from Egypt have acted corruptly. They have turned aside quickly out of the way that I commanded them; they have made themselves a metal image.’ “Furthermore, the LORD said to me, ‘I have seen this people, and behold, it is a stubborn people. Let me alone, that I may destroy them and blot out their name from under heaven. And I will make of you a nation mightier and greater than they.’ So I turned and came down from the mountain, and the mountain was burning with fire. And the two tablets of the covenant were in my two hands. And I looked, and behold, you had sinned against the LORD your God. You had made yourselves a golden calf. You had turned aside quickly from the way that the LORD had commanded you.
That the Israelites might have no pretence to think that God brought them to Canaan for their righteousness, Moses shows what a miracle of mercy it was, that they had not been destroyed in the wilderness. It is good for us often to remember against ourselves, with sorrow and shame, our former sins; that we may see how much we are indebted to free grace, and may humbly own that we never merited any thing but wrath and the curse at God’s hand. For so strong is our propensity to pride, that it will creep in under one pretence or another. We are ready to fancy that our righteousness has got for us the special favour of the Lord, though in reality our wickedness is more plain than our weakness. But when the secret history of every man’s life shall be brought forth at the day of judgment, all the world will be proved guilty before God. At present, One pleads for us before the mercy-seat, who not only fasted, but died upon the cross for our sins; through whom we may approach, though self-condemned sinners, and beseech for undeserved mercy and for eternal life, as the gift of God in Him. Let us refer all the victory, all the glory, and all the praise, to Him who alone bringeth salvation. (Henry)
The Israelites had witnessed firsthand the miracles, wonders, and signs of God. They partook of food and water that He supplied. They were able to see His closeness on the mountain, and yet, within 40 days they had turned from God as if what He had said, what He had done, and what He expected were as if it were nothing at all.
It is good to remind ourselves of the sinfulness of our sin and the undeserved grace and mercy given to us by God. This is not to be a trivial thought but an explosion and ever-life-changing continual meditation.