The Gospel Paul Preached
The Apostle Paul says God had chosen the Thessalonians (and us) and "called you by our gospel to the obtaining of the glory of our Lord Jesus Christ" (2TH.2:14). God chose to save those who obey (HEB.5:9) "our" gospel -- meaning the gospel which Paul and others like him preached. It is important, then, to know the characteristics of that gospel, and to respond to its call. The Galatians letter sets forth these characteristics.
In GAL.1:8 we learn that it is an exclusive, final gospel. "Though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed" Vs. 9 repeats this, giving greater emphasis than I could write.
GAL.1:11-24 states that this is a revealed gospel. It is not from within, not from among, but from above man. This gospel is not a social development; it is not the product of man's wisdom. Its essence had to be sent from heaven, by the Holy Spirit; and since it is final, we need expect no further revelation -- and certainly no different revelation today.
The gospel Paul preached was and is uncompromising. When its principle (one truth for all) was at stake, HEI"we gave place by subjection, no, not for an hour" (GAL.2:3-5). When the apostle Peter, through human weakness, "walked not uprightly according to the truth of the gospel" Paul "withstood him to the face, because he was to be blamed" (GAL.2:11-14). This gospel is a system of faith, as opposed to justification by law. GAL.3:10 explains what is meant by "justification by law" saying, "Cursed is every one that continueth not in all things which are written in the book of the law to do them". And again, (vs. 12). "The man that doeth them shall live in them". Law alone can justify only when its total requirements are met perfectly; there being no infraction, there can be no guilt. But no wholly mortal man has lived so perfectly; thus justification by law places us under a curse.
Now the gospel of Christ offers forgiveness through the offering of the perfect sacrifice, Jesus Christ. There is no less insistence upon obedience in the gospel of Christ (GAL.3:26-27; ROM.2:6-f; 2CO.5:10; 1PE.2:6-8 etc.) but when we have done all commanded, we are still unprofitable servants, needing Christ's forgiveness for our sins (LUK.17:10; ROM.4:6-8). There would not be so much confusion on these points if denominational preachers would quit inserting "only" after the word "faith", and would recognize the consistency of a "faith which works by love" (GAL.5:6).
Finally, the gospel Paul preached is a gospel of spirit versus flesh. It calls on us to put to death the fleshly desires that war against the spirit (COL.3:1-f). It names specific works of the flesh, and says, "they which do such things shall not inherit the kingdom of God" (GAL.5:16-26). It encourages us to bear the fruits of the Spirit.