Genesis 17:1-27
The LORD appears again to Abram, renews His promise of countless descendants and changes his name to Abraham. A change of name in the Bible is always a sign of a new relationship with the one who gives the new name. Here we see our patriarch as not only the man of faith but the father of all men of faith (Romans 4:11). In giving him this name "father of a multitude", God was already thinking with interest and love of this multitude of believers of which Abraham would be thought of as the head of the race and of which we hope all our readers form a part. And through the kings who will descend from Abraham, (v. 6) God was seeing in advance the "son of David", the King whom He was intending to send to Israel and to the world. The New Testament begins with the genealogy of Jesus Christ, son of David and son of Abraham.
At the same time as a name, God gives another sign to Abraham: that of circumcision, which corresponds in some degree to baptism today and represents both the setting apart for God and the lack of confidence in the flesh (Philippians 3:3).
The end of the chapter shows us Sarah also receiving a new name, the birth of Isaac foretold, then Abraham being obedient to the commandment God has given him.