There are four passages, all in the pastoral epistles, in which the apostle Paul says something is a “faithful saying.” A saying is a statement or expression which people think is significant enough to bear repetition and emphasis. A faithful saying is one upon which we can fully trust; it has proven itself to be true and dependable. Therefore, it is a saying that should be affirmed constantly and is worthy of all acceptation. Sadly, the faithful sayings that Christ spoke through Paul are neglected by most preachers and they are not accepted by the majority of people. But that does not change the truth that they express (Rom. 3:3-4).
Paul mentions three faithful sayings in his epistles to Timothy, and they correspond with the three major doctrines that Christ revealed through him and that are to be emphasized in this present age (see my post on the order of the church epistles): salvation in Christ (Romans), the Body of Christ (Ephesians), and the coming of Christ (Thessalonians).
I. Salvation (1 Tim. 1:15)
The Bible plainly teaches that all are sinners (Rom. 3:23) and that Christ is the only Savior (1 Tim. 2:4-7). You cannot be saved until you know that you are a lost sinner that needs to be saved. The good news of the gospel is that Christ died on the cross to pay for our sins, He was buried, and He rose again the third day for our justification (1 Cor. 15:3-4). We are saved totally by the grace of God without any works required to prove our faith (Eph. 2:8-9). This is the message we must faithfully preach to the world and it is worthy for all to accept.
In His earthly ministry, Christ was a minister of the circumcision confirming the promises made to their fathers (Rom. 15:8). He said, “I am not sent but unto the lost sheep of the house of Israel” (Matt. 15:24). He preached the gospel of the kingdom to Israel. It was God’s purpose and plan to use Israel as a kingdom of priests to reach the other nations, but He “came unto his own, and his own received him not” (Jn. 1:11). Christ prayed for His people on the cross (Lk. 23:34) and after His resurrection and ascension He sent the Holy Ghost with a renewed offer of the kingdom in early Acts. They rejected the Father throughout the OT, the Son in the Gospels, but it was when they rejected the witness of the Holy Ghost through the 12 apostles that they fell (Acts 7).
God could have poured out wrath, but instead He poured out grace. He saved the leader in the rebellion (Saul of Tarsus) against him and sent him to be the apostle to the Gentiles. Christ revealed through Paul that He came to save all sinners, and they can come directly to God without Israel. Notice the last phrase of this faithful saying ("of whom I am chief"). Most take this to mean that Paul felt he was the worst sinner. Perhaps he indeed felt that way, but chief does not mean worst. Paul is saying that he was the first sinner to be saved in the manner that he was (vs.11-17). He could not be saved under that gospel of the kingdom because he blasphemed the Holy Ghost (Matt. 12:31-32). He was saved by believing the gospel that Christ revealed to him (Gal. 1:11-12). There is a difference between finding grace in the eyes of the Lord (Gen. 6:8), and grace finding you.
II. Godliness (1 Tim. 4:8-9)
When you consider the context, you will understand how this faithful saying has to do with the Body of Christ (3:14-4:10). We are made godly by our union with Christ (3:16 is about the Body of Christ, that is why it is out of order, see my recent post about the mystery of godliness), not by the efforts of the flesh. To be in spiritual health we must have a balance between proper diet and exercise. Doctrine without duty is a tree without fruit, but duty without doctrine is a tree without roots. Living godly will bring persecution in this life (2 Tim. 3:12), but it will be worth it in the life to come.
III. Eternal Glory (2 Tim. 2:10-13)
All of the Body of Christ will be caught up in the rapture, but we will not all receive the same rewards at the Judgement Seat of Christ. We will all be glorified, but it is possible to obtain even more glory in our reign with Christ by faithful service. If you deny the truth in order to avoid suffering, Christ will deny you rewards in His heavenly kingdom. He will not deny us in salvation, because He cannot deny Himself and we are members of His Body.
We see all three issues mentioned in the last passage in which Paul mentions a "faithful saying" (Titus 3:3-8). I believe that the faithful saying in the passage is what he says in vs.4-7, and it is the faithful preaching of this glorious truth that will motivate believers to live a life of good works.