Christ's One Offering Sanctified forever those He died for !
So because Christ's Death alone has once and for all sanctified or set apart for God's Purpose all those he died for, as an evidence of that Truth, the Spirit of God gives New Life unto all of them unto Gospel Obedience or Belief of the Truth, or its called Sanctification of the Spirit unto belief of the Truth. This also answers the Redeemers prayer for all whom He died Jn 17:17-20
17 Sanctify them through thy truth: thy word is truth.
18 As thou hast sent me into the world, even so have I also sent them into the world.
19 And for their sakes I sanctify myself, that they also might be sanctified through the truth.
20 Neither pray I for these alone, but for them also which shall believe on me through their word;
1 Pet 1:2
2 Elect according to the foreknowledge of God the Father, through sanctification of the Spirit, unto obedience and sprinkling of the blood of Jesus Christ: Grace unto you, and peace, be multiplied.
The prep eis unto can mean into, so it could read:
2 Elect according to the foreknowledge of God the Father, through sanctification of the Spirit, into obedience and sprinkling of the blood of Jesus Christ: Grace unto you, and peace, be multiplied.
Now this sanctifying work of the Spirit unto Gospel obedience, is the FRUIT of Christ's Death, His One offering of Heb 10:10 ! All Persons Christ died for are automatically Sanctified [once and for all] by the Divine Purpose, even before actual childbirth as sinners, even as Jeremiah was Jer 1:5
5 Before I formed thee in the belly I knew thee; and before thou camest forth out of the womb I sanctified thee, and I ordained thee a prophet unto the nations.
Yet, this did not mean that Jeremiah would not still be born a sinner, a child of wrath by nature as others, and not needing to be born again, but all that would occur by the Divine Purpose in due time so that he could fulfill his call as a prophet. However in God's Purpose, Jeremiah was always sanctified and set apart for God's Holy Purpose, his being born a sinner could not thwart that Purpose, neither for any other person Christ died for and set them apart for God's Holy Purpose in the Body of Christ. It is simply impossible for anyone Christ died for to not in time be sanctified by the Spirits Work unto obedience so they can perform the works God hath already ordained before that they should walk in Eph 2:8-10147
8 For by grace are ye saved through faith; and that not of yourselves: it is the gift of God:
9 Not of works, lest any man should boast.
10 For we are his workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them.