He communicates the Covenant Promises !
Eternal Salvation, or Eternal life is premised upon a Promise, a Covenant Promise centered in the Blood of Jesus Christ. For His Precious blood gives Life ! He was given as Covenant to the People Isa 42:6
I the LORD have called thee in righteousness, and will hold thine hand, and will keep thee, and give thee for a covenant of the people, for a light of the Gentiles;
Based upon the Fact that Jesus Christ has met all the conditions and fulfilled them all for those He was given as a Covenant both of the Jews and Gentiles, they receive Life, Eternal Life through Him Rom 6:23
23For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord.
This Gift of Eternal Life through Him is no more an offer than the wages of sin was an offer. The wages of sin , death was merited through our disobedience in Adam, and likewise, Eternal Life was merited for those Christ represented by his obedience. Just as a corrupted Physical life is communicated because of our disobedience in Adam, so a Spiritual and Eternal Life is communicated because of the Covenant keeping obedience of Jesus Christ !1
It is the Holy Spirit that implements the Covenant Promise to the Elect of God through Jesus Christ Isa 54:13
13And all thy children shall be taught of the LORD; and great shall be the peace of thy children.
So Jesus says to the Representatives of the Elect Church, His Apostles these words Jn 14:26
26But the Comforter, which is the Holy Ghost, whom the Father will send in my name, he shall teach you all things, and bring all things to your remembrance, whatsoever I have said unto you.
The Holy Ghost will be sent in Christ Name, that is based upon His Finished work, His redemptive work of the Cross, and Teach the Church, those He gave Himself for Eph 5:25 all things, that is all things in regards to Christ accomplishments on their behalf through His blood. Yes, I know this was specifically said to the disciples, but they stood for His Church, All that should believe on Him through their word Jn 17:20
20Neither pray I for these alone, but for them also which shall believe on me through their word;
Did not John write to ordinary believers in His 1 Epistle 1 Jn 2:27,20
20But ye have an unction from the Holy One, and ye know all things.
27But the anointing[The Holy Spirit] which ye have received of him abideth in you, and ye need not that any man teach you: but as the same anointing teacheth you of all things, and is truth, and is no lie, and even as it hath taught you, ye shall abide in him.
See the similarity this verse has with what Jesus promised in Jn 14:26 ?
He shall teach you all things ? So 1 Jn 2:27 is the fulfillment of the Promise Jesus made to The Church represented by His Twelve Chosen Apostles in Jn 14:26. And this be the fulfillment of the Covenant Promise of Isa 54:13 which is the result of Christ being given as a Covenant to the People Isa 42:6.
So this Teaching work of the Spirit in an inner work and is the outcome of a Covenant Promise, which was based upon the Blood of the Covenant, the Blood of Christ Matt 26:28 and Heb 13:20-21
20Now the God of peace, that brought again from the dead our Lord Jesus, that great shepherd of the sheep, through the blood of the everlasting covenant,
21Make you perfect in every good work to do his will, working in you that which is wellpleasing in his sight, through Jesus Christ; to whom be glory for ever and ever. Amen.
You see that ? Working in you ! The Holy Spirit must communicate Life, Spiritual life and begin His work in each soul Christ died for. Phil 1:6
6Being confident of this very thing, that he[The Spirit of God] which hath begun a good work in you will perform it until the day of Jesus Christ:
Paul could be confident of this, because he understood that these things were happening because of Faithfulness to the Everlasting Covenant, and the Spirits application of those Covenant promises..