If you are following along with the first readings from the Book of Genesis, you may notice that things progressively move from bad to worse.
In Genesis 3, Adam and Eve eat forbidden fruit
In Genesis 4, Cain murders his brother
Later in Genesis 4, Lamech murders someone and basically gloats about it
By Genesis 6, the whole earth is filled with violence
In Genesis 9, Noah squanders his fresh start by getting drunk and cursing one of his sons
In Genesis 11, the people get scattered because they try to build a tower to reach God
We can see in the overarching story the destructive effects of sin. Sin enters the world and things get progressively get worse. Sin is still this destructive force in our lives and in the church today. Of what do we need to repent?