“Take heed, brethren, lest there be in any of you an evil heart of unbelief, in departing from the living God.” – Hebrews 3:12
Two Scriptures in the Epistle to the Hebrews reveal in no uncertain terms that the eternal security of the Christian is conditional. This Epistle was written to real Christians, called holy brethren (3:1), who were persecuted and sorely tempted to turn away from Jesus Christ. They were told, “Cast not away therefore your confidence, which hath great recompence¹ of reward (10:36). Keeping this in mind, Hebrews 3:6 says, “But Christ as a son over his own house; whose house are we, if we hold fast the confidence and the rejoicing of the hope firm unto the end.” The Holy Spirit, the real Author of this Epistle, used the strong conditional word if here and in 3:14. It means if only or if indeed. The Christian must indeed hold fast (keep a tight grip on) the confidence that he or she has placed in Jesus Christ as Savior and in the rejoicing of the hope of His salvation; and this must be done until the end of life.
Hebrews 3:14 repeats the warning, “For we are made partakers of Christ, if we hold the beginning of our confidence stedfast² unto the end.” (Here again is the strong conditional if.) Partakers of Christ are real Christians — not just in name only. To be a partaker of Jesus Christ is to have an actual share in His salvation. This word partakers is used elsewhere in this Epistle in reference to real Christians: “partakers of the heavenly calling” (3:1); “partakers of the Holy Ghost” (6:4); “chastisement, whereof all are partakers” (12:8); “partakers of his holiness” (12:10). The Christian life consists of trials and temptations, hence the warning to remain steadfast in one’s confidence in Jesus until the end of life. Jesus has promised to every faithful Christian, “I will never leave thee, nor forsake thee” (Heb. 13:5b). While it was believed that a literal translation of this Scripture was hardly possible, it would nevertheless read like this: “No, I will not leave thee; no, neither will I not utterly forsake thee.” — Adam Clarke
“For ye have need of patience, that, after ye have done the will of God, ye might receive the promise.” – Hebrews 10:36
¹ or recompense
² or steadfast