In a recent sermon I made the case that the worst sin in the modern world is the sin of living as if God is irrelevant. Another name for this is unbelief. Yet another biblical way to describe it is forgetting God.
God’s people were exhorted not to forget Him in the Law.
Take care lest you forget the LORD, who brought you out of the land of Egypt, out of the house of slavery. (Deuteronomy 6:12)
The history books of the Old Testament record forgetfulness.
The people of Israel did what was evil in the sight of the LORD. They forgot the LORD their God and served the Baals and Asheroth. (Judges 3:7)
Not only the Jews, but all peoples were threatened about forgetfulness in the writings.
the wicked shall return to Sheol,
all the nations that forget God. (Psalm 9:17)
Mark this, then, you who forget God,
lest I tear you apart, and there be none to deliver! (Psalm 50:22)
The prophets also admonish the forgetful:
For you have forgotten the God of your salvation and have not remembered the Rock of your refuge; (Isaiah 17:10)
I, I am he who comforts you;
who are you that you are afraid of man who dies,
of the son of man who is made like grass,
and have forgotten the LORD, your Maker,
who stretched out the heavens and laid the foundations of the earth. (Isaiah 51:12-13)
Murder, theft, adultery, lying, coveting, homosexuality, idolatry, and forgetfulness of our Maker, these are all sins. Which means that Jesus had to die for our forgetfulness. But also, Jesus died for our forgetfulness. Let us not forget that.