God is angry with Moses because he is disobedient. God has ordered to circumcise boys on the eighth day. It was the sign of the covenant with God (Genesis 17:10). Circumcision is a sign which means that that child belongs to God, is God’s child. When someone is disobedient, he has to be cut off from the covenant because he has broken the covenant (Genesis 17:14). That means the death penalty. God is also angry because Moses is not credible. How can he speak (in God’s name) to Pharaoh: let my son go,
and meanwhile hold his own son away from God? Moses has to circumcise his heart, as he later tells Israel (Deuteronomy 10:16). God prepares him to rescue God’s firstborn.
24 At a lodging place on the way the LORD met him and sought to put him to death.