Ephesians 1:3

He begins with thanksgivings and praise, and enlarges with a great deal of fluency and copiousness of affection upon the exceedingly great and precious benefits which we enjoy by Jesus Christ. For the great privileges of our religion are very aptly recounted and enlarged upon in our praises to God. I. In general he blesses God for spiritual blessings, Eph 1:3, where he styles him the God and Father of our Lord Jesus Christ; for, as Mediator, the Father was his God; as God, and the second person in the blessed Trinity, God was his Father. It bespeaks the mystical union between Christ and believers, that the God and Father of our Lord Jesus Christ is their God and Father, and that in and through him. All blessings come from God as the Father of our Lord Jesus Christ. No good can be expected from a righteous and holy God to sinful creatures, but by his mediation. He hath blessed us with all spiritual blessings. Note, Spiritual blessings are the best blessings with which God blesses us, and for which we are to bless him. He blesses us by bestowing such things upon us as make us really blessed. We cannot thus bless God again; but must do it by praising, and magnifying, and speaking well of him on that account. Those whom God blesses with some he blesses with all spiritual blessings; to whom he gives Christ, he freely gives all these things.

— Matthew Henry's Concise Commentary (public domain)

The doxologies in almost all the Epistles imply the real sense of grace experienced by the writers and their readers (Pe1 1:3). Eph 1:3-14 sets forth summarily the Gospel of the grace of God: the FATHER'S work of love, Eph 1:3 (choosing us to holiness, Eph 1:4; to sonship, Eph 1:5; to acceptance, Eph 1:6): the SON'S, Eph 1:7 (redemption, Eph 1:7; knowledge of the mystery of His will, Eph 1:9; an inheritance, Eph 1:11); the HOLY SPIRIT'S, Eph 1:13 (sealing, Eph 1:13; giving an earnest of the inheritance, Eph 1:14). the God and Father of . . . Christ--and so the God and Father of us who are in Him (Joh 20:17). God is "the God" of the man Jesus, and "the Father" of the Divine Word. The Greek is, "Blessed us," not "hath blessed us"; referring to the past original counsel of God. As in creation (Gen 1:22) so in redemption (Gen 12:3; Mat 5:3-11; Mat 25:34) God "blesses" His children; and that not in mere words, but in acts. us--all Christians. blessings--Greek, "blessing." "All," that is, "every possible blessing for time and eternity, which the Spirit has to bestow" (so "spiritual" means; not "spiritual," as the term is now used, as opposed to bodily). in heavenly places--a phrase five times found in this Epistle, and not elsewhere (Eph 1:20; Eph 2:6; Eph 3:10; Eph 6:12); Greek, "in the heavenly places.

— Jamieson-Fausset-Brown Commentary (public domain)