Ezekiel 36.27

In Ezekiel 36:27 it says we will receive the Holy Spirit in our spirit. In the OT the Holy Spirit never dwelt in believers for this was never available in the Old Covenant. The Holy Spirit came upon men but in those days the Holy Spirit never dwelt in men forever.

How do we know the Holy Spirit will dwell in us believers forever?
John 14:16-17.

The "he" in v.16 is the "I" in vs.18 showing that the Comforter is but the Lord coming in another form "come unto you" (v.18). Who can deny this?

The "another Comforter" is but the Lord Jesus coming in a different form. Just as God comes among men in and through Christ, so Christ comes into men in and through the Holy Spirit. Christ was clothed with the Holy Spirit and could consequently dwell in men.

The Holy Spirit is the same in us as Christ in us.

Rom 8:9 But ye are not in the flesh, but in the Spirit, if so be that the Spirit of God dwell in you. Now if any man have not the Spirit of Christ, he is none of his.
2Cr 13:5 Examine yourselves, whether ye be in the faith; prove your own selves. Know ye not your own selves, how that Jesus Christ is in you, except ye be reprobates?

Eph 3:17 That Christ may dwell in your hearts by faith; that ye, being rooted and grounded in love,

The God in 3:19 is the Christ in 3:17.

Eph 3:19 And to know the love of Christ, which passeth knowledge, that ye might be filled with all the fulness of God.