When Simeon and Levi used circumcision (the sign of God’s covenant) to deceive and kill the Canaanite men, they showed disrespect for that sacred sign. Their killing of all the males and their looting of the city was not justice. It was harsh and excessive revenge.
They were angry and wanted to correct a wrong. But they should have asked for payment for the harm done (see Exodus 22:16–17; Deuteronomy 22:28–29). Instead, their violent anger led to the loss of their birthright blessing (the special family blessing given to the firstborn; Genesis 49:5–7).