The Bible teaches that, contrary to what some of us have been taught in the past, in one sense we are already sanctified – 1 Co 1:2 Unto the church of God which is at Corinth, to them that are sanctified in Christ Jesus, called to be saints, 1 Co 6:11 but ye are washed, but ye are sanctified, but ye are justified in the name of the Lord Jesus, and by the Spirit of our God. Heb 10:10 By the which will we are sanctified through the offering of the body of Jesus Christ once for all. Heb 13:12 Wherefore Jesus also, that he might sanctify the people with his own blood, suffered without the gate. Jude 1:1 Jude, the servant of Jesus Christ, and brother of James, to them that are sanctified by God the Father, and preserved in Jesus Christ, and called.
So we can see that a past sanctification is taught in Scripture.
In Jn 17:17 Jesus says “sanctify them through thy truth; thy word is truth“ – Jesus is speaking here of his disciples being sanctified, not the world. In 1 Cor 1:30, Eph 5:26, Paul says “Christ loved the church and gave himself for it, that he might sanctify and cleanse it” – so it is the church that is cleansed and sanctified, not the world. In 2 Tim 2:21 “If a man purge himself from these…he shall be sanctified” – this does not say the whole world will be sanctified, but those who purge themselves, clearly referring to believers. In Heb 10:10 “We are sanctified through the offering of
the body of Jesus Christ” – who is the “we”? It is believers, not the whole world. In 1 Peter 1:2 “elect…through sanctification, unto obedience” – again this is to believers – the whole world is not the elect. In 1 Thess 4:3 and 5:23 sanctification even seems to be a process, and this book again is not written to unbelievers but to believers. Search the scriptures as much as you like, but you will not find any scriptures that say what GCI says, that the whole world was sanctified, which yet again is universalism. No, believers are sanctified, not the whole world.
The Bible is clear that because of the finished work of Christ on the cross, we are already made holy. For example, consider the following Scriptures: Col 1:22 In the body of his flesh through death, to present you holy and unblameable and unreproveable in his sight. 1 Cor 3:17 If any man defile the temple of God, him shall God destroy; for the temple of God is holy, which temple ye are. Heb 3:1 Wherefore, holy brethren, partakers of the heavenly calling, consider the Apostle and High Priest of our profession, Christ Jesus; 1Pe 2:5 Ye also, as lively stones, are built up a spiritual house, an holy priesthood, to offer up spiritual sacrifices, acceptable to God by Jesus Christ. 1 Pe 2:9 But ye are a chosen generation, a royal priesthood, an holy nation, a peculiar people; that ye should shew forth the praises of him who hath called you out of darkness into his marvelous light: Also note that it is only God who is holy – it is really only God dwelling in us that makes us holy. Re 15:4 Who shall not fear thee, O Lord, and glorify thy name? for thou only art holy.
There are also other verses that imply a future or process of sanctification and becoming holy – see https://word.spiritbodysoul.com/sanctification-process.
Its interesting that the issue of whether sanctification was accomplished through what Jesus did on the cross and was available to the believer as soon as they believe or was a subsequent experience to salvation (a “second work of grace”) caused a huge split in the Azusa Street Revival. See for example http://www.revival-library.org/pensketches/am_pentecostals/durham.html
‘William Durham… began a preaching mission at the Upper Room Mission in Los Angeles but, despite his brilliant oratory and pulpit presence, the congregation ejected him over sanctification teaching of the “Finished Work.” This teaching repudiated the holiness doctrine of sanctification as a second work of grace and instead declared that everything a believer would ever need was included in the finished work of Christ on the cross. This repudiation of the Holiness doctrine of sanctification as a “second work of grace,” argued that the “finished work” of Christ on Calvary becomes available to the believer at the time of justification. The benefits of Calvary are therefore appropriated for sanctification over the entire period of the Christian’s life, rather than at a single subsequent moment, as was believed by most Pentecostals in Durham’s day. ‘