In this epistle, St. Paul first teaches what the gospel is, how it alone was provided by God in unity, and how it was earned and originated through Christ, so that all who believe in it may become righteous, godly, alive, blessed, and free from the law, sin, and death. He does this through the first three chapters.
(2) Then he teaches us to avoid the secondary doctrines and the commandments of men, so that we may be bound to One.
To abide in the head, to be sure, to become righteous and complete in Christ alone, in whom we have nothing apart from him. He teaches this in the fourth chapter.
3 Henceforth he teaches to exercise and prove faith with good works, and to avoid sin, and to fight against the devil with spiritual weapons, so that through the cross we may stand in hope.