The Greek word for “establish” is STERIZO and it means, “to make fast, to confirm, to strengthen.” Once a person is saved he/she needs to be “confirmed in the faith.” It’s important to see that “the faith” is NOT one’s personal faith in the Lord Jesus Christ; it is all “the truth” concerning the Person and Work of Christ. In Jude 3 we are told to “contend earnestly for THE FAITH which was once for all delivered to the saints.” Yet in order to “contend for THE FAITH,” one must be “established (confirmed) in the faith.”

Now for your question, “Who is supposed to establish the saints in the faith?” In writing to the church at Rome the Apostle Paul said, “I long to see you, that I may impart some spiritual gift, so that YOU MAY BE ESTABLISHED” (Romans 1:11). The word “impart” means “to share” and thus Paul was saying, “I want to share with you what the Lord has given to me so that you will be established.” What had the Lord given to Paul? Ah, He had given to Paul ALL THE TRUTH concerning the Person and Work of Christ! Paul had received many revelations about Jesus Christ (see Galatians 1:12; 2nd Corinthians 12:1) and one of the greatest is mentioned in Ephesians 3:3-5, “How that by REVELATION He made known to me the mystery (as I have briefly written already, by which, when you read, you may understand my knowledge in the mystery of Christ), which in other ages was not made known to the sons of men, as IT HAS NOW BEEN REVEALED BY THE SPIRIT TO HIS HOLY APOSTLES AND PROPHETS.” Paul was an apostle who was given knowledge (i.e. truth) about Jesus Christ that had not been revealed before. After it was revealed to him HE TAUGHT IT TO OTHERS! And in doing so he would be “establishing the saints in the faith.” So, in answer to your question, it is primarily the “apostles and prophets” who established the churches and they did this by teaching the saints the truth about Jesus Christ. This is why they are mentioned first in Ephesians 4:11, “And He (Jesus Christ) gave some as APOSTLES, and some as PROPHETS” (NASB).

Let’s look at a few more scriptures which bring this out. In Ephesians 2:19-20 Paul said, “Now, therefore, you are no longer strangers and foreigners, but fellow citizens with the saints and members of the household of God, HAVING BEEN BUILT ON THE FOUNDATION OF THE APOSTLES AND PROPHETS, Jesus Christ Himself being the chief corner stone.” When Paul taught the saints the truth about Jesus Christ he was giving them all the FOUNDATIONAL TRUTHS they needed to be “confirmed in the truth.” It is vital to see this, for Jesus Christ is the ROCK upon which the church is being built (see Matthew 16:13-17 and 1st Peter 2:4-7a) and so we must know who He is and what He has done in order to be truly “established in the faith.” Again, God was pleased to give all this truth to the Apostle Paul (and other apostles and to prophets) so they could LAY THE FOUNDATION OF TRUTH that would result in our being “strengthened in the truth.”

Another passage that teaches us this is 1st Corinthians 3:10-11 where Paul says, “According to the grace of God which was given to me, AS A WISE MASTER BUILDER I HAVE LAID THE FOUNDATION, and another builds on it. But let each one take heed how he builds on it. For no other foundation can anyone lay that that which is laid, which is Jesus Christ.” Notice, Paul speaks of himself as “a wise master builder” who laid the foundation but then he goes on to speak of how “another builds on it.” What does that mean? It means that once we have learned the wonderful foundational truths about Jesus Christ we should TEACH THEM TO OTHERS! This doesn’t mean we are “laying the foundation,” for a foundation is only laid once and the Apostle Paul did that. It means that we “build on that foundation” by teaching other believers what the Apostle Paul has taught us. In that sense we too have the privilege (and responsibility) to “establish the saints in THE FAITH.  (405.3)  (DO)