The Apostle Paul
Ephesians 1:4BSB·traditional attribution

For He chose us in Him before the foundation of the world to be holy and blameless in His presence. In love

Geneva Bible Notes Reformed

According as he hath chosen us in him before the foundation of the world, that we should be holy and without blame before him in love: (6) He declares the efficient cause, or by what means God the Father saves us in his Son: because, he says, he chose us from everlasting in his Son. (d) To be adopted in him.

Jamieson-Fausset-Brown Reformed

hath chosen us--Greek, "chose us out for Himself" (namely, out of the world, Gal 1:4): referring to His original choice, spoken of as past. in him--The repetition of the idea, "in Christ" (Eph 1:3), implies the paramount importance of the truth that it is in Him, and by virtue of union to Him, the Second Adam, the Restorer ordained for us from everlasting, the Head...

John Gill Reformed Baptist

According as he hath chosen us in him,.... This choice cannot be understood of a national one, as Israel of old were chosen by the Lord; for the persons the apostle writes to were not a nation; nor does he address all the inhabitants of Ephesus, only the saints and faithful in Christ that resided there; nor are they all intended here, if any of them.