Genesis 17 Commentary

When Abram was 99 years old, God established a covenant with him to bless him greatly if he walked blameless. God expanded His covenant to add this mutual condition, where Abram would receive blessings if he walked in righteousness. 

God changes Abram’s name to Abraham because he will be the father of many nations.

God promises that many nations and kings will come from Abraham’s descendants. God's covenant is never-ending, and He promises to give the land of Canaan as a perpetual possession to Abraham's descendants. God also indicates that His covenant extends to Abraham's descendants after him. This would include the benefit of the rewards already granted as well as the conditional promise to bless them when they live faithfully. 

God commands Abraham that every male who keeps the covenant must be circumcised as a sign of the covenant.

God gives further instructions about circumcision; Male babies who are 8 days old, even servants either born or bought must be circumcised. Anyone who is not circumcised has broken God's covenant.

God changes Sarai’s name to Sarah and promises she will birth a son. Abraham laughed that a man 100 and his wife 90 years old could have a child.

Abraham presumes God meant that His promises to bless him and his descendants would come through Ishmael.

When God had finished talking, Abraham immediately took all the males in his household and circumcised them as God had commanded.