But he that shall endure to the end, the same shall be saved. (Matt 24:13)
This verse may trouble many persons or at least may mislead them, if it is not understood in its context. This scripture does not refer to the present age at all, as the context will show, but to the future tribulation period, during which many will suffer the martyrs death (Rev. 10, 11; 20:4) and be taken to heaven while others will be saved through the tribulation to enter the kingdom on earth (Rev 7:1-8). It is also important to realize that this is after the church is caught up, and is related to the time of God's judicial and age ending dealings with Israel and the Nations.
But there are other scriptures that sound like this, such as Colossians 1:23, for instance: "if ye continue in the faith, grounded and settled," etc. All scripture is given by inspiration of God but such portions should not be used to unsettle souls as to the certainty of their life in Christ (Col. 3:3; Eph. 4:30, Rom 8:28-29). It may be used to exercise a true believer, but those who believe to the salvation of their souls do not draw back unto perdition (Heb 10:39) and their continuance only proves the reality of their standing. 2 Peter 2:22 is true, and so is John 10:28. One is mere profession and the other is true profession.