It is not just a handful of texts that teach the perseverance of the saints: the entire gospel sustains and confirms it. The Father has chosen them before the foundation of the world (Eph. 1:4), ordained them to eternal life (Acts 13:48), to be conformed to the image of his Son (Rom. 8:29). This election stands (Rom. 9:11; Heb. 6:17) and in due time carries with it the calling and justification and glorification (Rom. 8:30). Christ, in whom all the promises of God are Yes and Amen (2 Cor. 1:20), died for those who were given him by the Father (John 17:6, 12) in order that he might give them eternal life and not lose a single one of them (6:40; 17:2); he therefore gives them eternal life and they will never be lost in all eternity; no one will snatch them out of his hand (6:39; 10:28).
The Holy Spirit who regenerates them remains eternally with them (14:16) and seals them for the day of redemption (Eph. 1:13; 4:30). The covenant of grace is firm and confirmed with an oath (Heb. 6:16–18; 13:20), unbreakable like a marriage (Eph. 5:31–32), like a testament (Heb. 9:17), and by virtue of that covenant, God calls his elect. He inscribes the law upon their inmost being, puts his fear in their heart (Heb. 8:10; 10:14ff.), will not let them be tempted beyond their strength (1 Cor. 10:13), confirms and completes the good work he has begun in them (1 Cor. 1:9; Phil. 1:6), and keeps them for the return of Christ to receive the heavenly inheritance (1 Thess. 5:23; 2 Thess. 3:3; 1 Pet. 1:4–5).
In his intercession before the Father, Christ acts in such a way that their faith may not fail (Luke 22:32), that in the world they may be kept from the evil one (John 17:11, 20), that they may be saved for all times (Heb. 7:20), that their sins will be forgiven them (1 John 2:1), and that they may all be where he is to behold his glory (John 17:24). The benefits of Christ, which the Holy Spirit imparts to them, are all irrevocable (Rom. 11:29). Those who are called are also glorified (8:30). Those who are adopted as children are heirs of eternal life (8:17; Gal. 4:7). Those who believe have eternal life already here and now (John 3:16). That life itself, being eternal, cannot be lost. It cannot die since it cannot sin (1 John 3:9). Faith is a firm ground (Heb. 11:1), hope is an anchor (6:19) and does not disappoint us (Rom. 5:5), and love never ends (1 Cor. 13:8).
– Herman Bavinck, Reformed Dogmatics: Holy Spirit, Church, and New Creation, vol. 4