1 Corinthians 15:3

I delivered unto you--A short creed, or summary of articles of faith, was probably even then existing; and a profession in accordance with it was required of candidates for baptism (Act 8:37). first of all--literally, "among the foremost points" (Heb 6:2). The atonement is, in Paul's view, of primary importance. which I . . . received--from Christ Himself by special revelation (compare Co1 11:23). died for our sins--that is, to atone FOR them; for taking away our sins (Jo1 3:5; compare Gal 1:4): "gave Himself for our sins" (Isa 53:5; Co2 5:15; Tit 2:14). The "for" here does not, as in some passages, imply vicarious substitution, but "in behalf of" (Heb 5:3; Pe1 2:24). It does not, however, mean merely "on account of," which is expressed by a different Greek word (Rom 4:25), (though in English Version translated similarly, "for"). according to the scriptures--which "cannot be broken." Paul puts the testimony of Scripture above that of those who saw the Lord after His resurrection [BENGEL]. So our Lord quotes Isa 53:12, in Luk 22:37; compare Psa 22:15, &c.; Dan 9:26.

— Jamieson-Fausset-Brown Commentary (public domain)