Certain crucial theological words, describing important biblical truths, do not appear in the English Bible. You know about the words “Trinity,” “rapture,” and “worldliness.” Another word not in there is “apostasy.” The English term sounds like “apostle,” and they relate.
The one and true God sent an apostle and he continued in the way God sent him. An apostle is in a literal sense, a sent one. On the other hand, an apostate turns from the faith. He departs from God’s way. He defects from a genuine Christian life.
In Jude 1:3, Jude writes: “ye should earnestly contend for the faith which was once delivered unto the saints.” Genuine believers in Jesus Christ contend for the faith so that others will not turn from the faith, which is to apostatize. When a professing believer defects from the faith, this is apostasy. Maybe you are a Christian parent reading this, thinking about your children. Of anyone, you don’t want your children to apostatize, that is, leave the faith in which you trained them.
The entire second epistle of Peter addresses apostasy. The one sure safeguard against apostasy is a true conversion experience. Those truly saved cannot and will not leave the faith (2 Peter 1:1-12, John 10:27-29). If someone does “leave the faith,” it’s because he was never saved in the first place. Like 1 John 2:19 says, “if they had been of us, they would no doubt have continued with us.”