The form of the doxology may have been taken from its liturgical use in apostolic times (cf. Jas 3:9). The doxology is offered for the regeneration of Christians through Jesus Christ unto eternal salvation: “who according to His great mercy has begotten us again,” and so forth.
Mercy is the merciful love of God toward the weak, helpless, powerless, and sinful, as all people are outside the grace of regeneration.
The salvation of the world through Christ is exclusively the work of God’s love for the world (Jn 3:16). More precisely, it is the work of merciful, condescending, and forgiving love.
Man himself, because of his sinfulness and impurity after falling away from God, is unworthy of God’s love for him and has no claim to it.
This merciful love of God the Father sent His beloved Son into the world for the redemption of the world and the regeneration of those who believe in Him into new life.
“Who has begotten us again” means who has spiritually born us anew from above (cf. Jn 3:3; Tit 3:5; Col 3:1; Eph 1:19-20; Eph 2:10).
All who do not believe in the Lord Jesus Christ as Redeemer of the world are not regenerated, although Christ’s sacrifice on the Cross extends to all. To believers a new spiritual beginning of life is given in the mysteries of baptism and chrismation.
It is also given in the other varied actions of the grace of the Holy Spirit, which make the human soul alive.
In falling away from God, man is spiritually dead. Faith in Christ makes him alive, as though it gives him birth anew.
Thus, in union of life with Christ, he may attain his highest calling, which was originally proper to his nature but was lost by him. This calling is eternal blessedness.
This goal of regeneration is indicated in the words: “unto a living hope.” We are saved in hope, says another apostle (Rom 8:24).
Now, in this life, the believer in Christ only hopes for his salvation. Possession of it belongs to the future. This hope for salvation is given by regeneration and in regeneration.
Without regeneration there is no hope for salvation. Thus the believer is begotten again unto hope.
This hope of the regenerate is a living hope. What arises through birth is living. So also the hope of the regenerate is living, in contrast to the dead, powerless, vain, and empty hope of the unregenerate people of this world.
Christian hope gives life to the spirit, because it consoles, strengthens, and gladdens it even in sufferings themselves.
“Through the resurrection of Jesus Christ.” According to the Greek construction, where this expression stands after “unto a living hope,” it can be related either to “has begotten us again” or to “living.”
In the first case it means that Christ’s resurrection is the means by which God has begotten us again unto a living hope. It is the fact that forms the living foundation of our living hope.
For the resurrection of Christ from the dead is the fundamental and central dogma of the faith that regenerates us (cf. Rom 10:9). If Christ has not risen, then our faith is vain.
Our hope is vain, and the preaching of the Gospel is vain (1 Cor 15:14, 17).
In the latter case, the expression means that the living character of the Christian hope to which they are begotten again rests on the resurrection of Jesus Christ. If Christ had not risen, this hope would not be living.
The latter thought has its basis in the first, as the particular in the general, or as the subordinate in the principal. Therefore the first interpretation should be preferred to the latter.
Or better, they should be joined together as mutually completing one another.
“Hope is living. From where does it have life? From the resurrection of Jesus Christ from the dead. For as He Himself rose, so He also gives to those who come to Him through faith in Him the same power to rise” (Theophylact).