1 Peter 1:3

We come now to the body of the epistle, which begins with, I. A congratulation of the dignity and happiness of the state of these believers, brought in under the form of a thanksgiving to God. Other epistles begin in like manner, Co2 1:3; Eph 1:3. Here we have, 1. The duty performed, which is blessing God. A man blesses God by a just acknowledgment of his excellency and blessedness. 2. The object of this blessing described by his relation to Jesus Christ: The God and Father of our Lord Jesus Christ. Here are three names of one person, denoting his threefold office. (1.) He is Lord, a universal king or sovereign. (2.) Jesus, a priest or Saviour. (3.) Christ, a prophet, anointed with the Spirit and furnished with all gifts necessary for the instruction, guidance, and salvation of his church. This God, so blessed, is the God of Christ according to his human nature, and his Father according to his divine nature. 3. The reasons that oblige us to this duty of blessing God, which are comprised in his abundant mercy. All our blessings are owing to God's mercy, not to man's merit, particularly regeneration.

— Matthew Henry's Concise Commentary (public domain)

He begins, like Paul, in opening his Epistles with giving thanks to God for the greatness of the salvation; herein he looks forward (1) into the future (Pe1 1:3-9); (2) backward into the past (Pe1 1:10-12) [ALFORD]. Blessed--A distinct Greek word (eulogetos, "Blessed BE") is used of God, from that used of man (eulogemenos, "Blessed IS"). Father--This whole Epistle accords with the Lord's prayer; "Father," Pe1 1:3, Pe1 1:14, Pe1 1:17, Pe1 1:23; Pe1 2:2; "Our," Pe1 1:4, end; "In heaven," Pe1 1:4; "Hallowed be Thy name," Pe1 1:15-16; Pe1 3:15; "Thy kingdom come," Pe1 2:9; "Thy will be done," Pe1 2:15; Pe1 3:17; Pe1 4:2, Pe1 4:19; "daily bread," Pe1 5:7; "forgiveness of sins," Pe1 4:8, Pe1 4:1; "temptation," Pe1 4:12; "deliverance," Pe1 4:18 [BENGEL]; Compare Pe1 3:7; Pe1 4:7, for allusions to prayer. "Barak," Hebrew "bless," is literally "kneel." God, as the original source of blessing, must be blessed through all His works. abundant--Greek, "much," "full." That God's "mercy" should reach us, guilty and enemies, proves its fulness. "Mercy" met our misery; "grace," our guilt. begotten us again--of the Spirit by the word (Pe1 1:23); whereas we were children of wrath naturally, and dead in sins. unto--so that we have. lively--Greek, "living." It has life in itself, gives life, and looks for life as its object [DE WETTE]. Living is a favorite expression of Peter (Pe1 1:23; Pe1 2:4-5). He delights in contemplating life overcoming death in the believer. Faith and love follow hope (Pe1 1:8, Pe1 1:21-22).

— Jamieson-Fausset-Brown Commentary (public domain)