Till we all come in the unity of the faith, and of the knowledge of the Son of God, unto a perfect man, unto the measure of the stature of the fullness of Christ" (Ephesians 4:13).
Don Calloway writes in the "Doctrinal Discussion" for this week's lesson...

Jesus prayed for unity among His disciples in His high priestly prayer found in John 17. He prayed for unity so that the world would recognize that He came from the Father. The implication seems to be that if Christ’s disciples are not in unity, the world will question the reliability of Christ’s claim to be God. Sadly, the world often has a clearer picture of the way things ought to be in the church than the church has! When we fail to demonstrate the unity existing between the Father and the Son, there is going to be a disconnect between our words and the message we send to the world.

Discussion: How should this scripture about the "unity of the faith" inform our prayers as a local church?
Source: Galatians and Ephesians: Adult Teacher's Insights, page 66.