You said: "not in some supernatural mystical way apart from His word".
I submit that you need to read and study your bible more.
From Charles Hodge's work "Systematic Theology, Volume 1, Theology Proper, Chapter VIII, Section II, The Holy Spirit, Sub-section B, The Spirits Office in the Work of Redemption, pp. 530-533", we read:
"With regard to the office of the Spirit in the work of redemption, the Scriptures teach, —
1. That He fashioned the body, and endued the human soul of Christ with every qualification for his work. To the Virgin Mary it was said,
“The Holy Ghost shall come upon thee, and the power of the Highest shall overshadow thee: therefore also that holy thing which shall be born of thee, shall be called the Son of God.” (
Luke i. 35.) The prophet Isaiah predicted that the Messiah should be replenished with all spiritual gifts. “Behold my servant whom I uphold; mine elect in whom my soul delighteth; I have put my Spirit upon him: he shall bring forth judgment to the Gentiles.” (
Is. xlii. 1.) “There shall come forth a rod out of the stem of Jesse, and a branch shall grow out of his roots: and the Spirit of the Lord shall rest upon him, the spirit of wisdom and understanding, the spirit of counsel and might, the spirit of knowledge and of the fear of the Lord.” (
Is. xi. 1, 2.) When our Lord appeared on earth,
it is said that the Spirit without measure was given unto Him. (
John iii. 34.) “And John bare record, saying, I saw the Spirit descending from heaven like a dove, and it abode upon him.” (
John i. 32.) He was, therefore, said to have been full of the Holy Ghost.
2. That the Spirit is the revealer of all divine truth.
The doctrines of the Bible are called the things of the Spirit. With regard to the writers of the Old Testament, it is said they spake as they were moved by the Holy Ghost. The language of Micah is applicable to all the prophets, “Truly I am full of power by the Spirit of the Lord, and of judgment, and of might, to declare unto Jacob his transgression and to Israel his sin.” (Micah iii. 8.) What David said, the Holy Ghost is declared to have said. The New Testament writers were in like manner the organs of the Spirit. The doctrines which Paul preached he did not receive from men “but God,” he says, “hath revealed them unto us by his Spirit.” (
1 Cor. ii. 10.) The Spirit also guided the utterance of those truths; for he adds, “Which things also we speak, not in the words which man’s wisdom teacheth, but which the Holy Ghost teacheth; communicating the things of the Spirit in the words of the Spirit” (πνευματικοῖς πνευματικὰ συγκρίνοντες). The whole Bible, therefore, is to be referred to the Spirit as its author.
3.
The Spirit not only thus reveals divine truth, having guided infallibly holy men of old in recording it, but He everywhere attends it by his power. All truth is enforced on the heart and conscience with more or less power by the Holy Spirit, wherever that truth is known. To this all-pervading influence we are indebted for all there is of morality and order in the world. But besides this general influence, which is usually called common grace, the Spirit specially illuminates the minds of the children of God, that they may knew the things freely given (or revealed to them) by God. The natural man does not receive them, neither can he know them, because they are spiritually discerned. All believers are therefore called (πνευματικοί) spiritual, because thus enlightened and guided by the Spirit.
4. It is the special office of the Spirit to convince the world of sin; to reveal Christ, to regenerate the soul, to lead men to the exercise of faith and repentance; to dwell in those whom He thus renews, as a principle of a new and divine life. By this indwelling of the Spirit, believers are united to Christ, and to one another, so that they form one body. This is the foundation of the communion of saints, making them one in faith, one in love, one in their inward life, and one in their hopes and final destiny.
5. The Spirit also calls men to office in the Church, and endows them with the qualifications necessary for the successful discharge of its duties. The office of the Church, in this matter, is simply to ascertain and authenticate the call of the Spirit. Thus the Holy Ghost is the immediate author of all truth, of all holiness, of all consolation, of all authority, and of all efficiency in the children of God individually, and in the Church collectively."
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If it is like you say: "not in some supernatural mystical way apart from His word", how do you explain so many of the OT writers?
"
The Spirit the Source of all Intellectual Life.
The Spirit is also represented as the source of all intellectual life. When man was created it is said God “breathed into his nostrils the breath of life; and man became (נֶפֶשׁ חַיָּה) a living soul.” (
Gen. ii. 7.)
Job xxxii. 8, says, The inspiration of the Almighty giveth men understanding, i.e., a rational nature, for it is explained by saying, He “teacheth us more than the beasts of the earth, and maketh us wiser than the fowls of heaven.” (
Job xxxv. 11.) The Scriptures ascribe in like manner to Him all special or extraordinary gifts. Thus it is said of Bezaleel, “I have called” him, “
and I have filed him with the Spirit of God, in wisdom, in understanding, and in knowledge, and in all manner of workmanship, to devise cunning works, to work in gold, and in silver, and in brass.” (
Ex. xxxi. 2, 3, 4.)
By his Spirit God gave Moses the wisdom requisite for his high duties, and when he was commanded to devolve part of his burden upon the seventy elders, it was said, “I will take of the Spirit which is upon thee, and will put it upon them.” (
Num. xi. 17.)
Joshua was appointed to succeed Moses, because in him was the Spirit. (
Num. xxvii. 18.) In like manner
the Judges, who from time to time were raised up, as emergency demanded, were qualified by the Spirit for their peculiar work, whether as rulers or as warriors. Of Othniel it is said, “The Spirit of the Lord came upon him, and he judged Israel and went out to war.” (
Judges iii. 10.) So the Spirit of the Lord is said to have come upon Gideon and on Jephthah and on Samson. When Saul offended God, the Spirit of the Lord is said to have departed from him. (
1 Sam. xvi. 14.) When Samuel anointed David, “The Spirit of the Lord came upon” him “from that day forward.” (
1 Sam. xvi. 13.) In like manner under the new dispensation the Spirit as represented as not only the author of miraculous gifts, but also as the giver of the qualifications to teach and rule in the Church. All these operations are independent of the sanctifying influences of the Spirit. When the Spirit came on Samson or upon Saul, it was not to render them holy, but to endue them with extraordinary physical and intellectual power; and when He is said to have departed from them, it means that those extraordinary endowments were withdrawn."
Ibid
To take it even further, we read:
"THE HOLY SPIRIT IS THE SANCTIFIER AND COMFORTER OF GOD'S PEOPLE.
[1]
The Holy Spirit is the author of holiness in all those who are saved: "Through sanctification of the Spirit."
[2] "Ye are washed, ye are sanctified by the Spirit of our God."
[3] He is the author of the new or spiritual life which is produced in regeneration.
[4] Not only the beginning of the new life, but its whole progress, is dependent on the Spirit: wherefore, believers are said to live in the Spirit,
[5] to walk in the Spirit, to be led by the Spirit,
[6] and be filled with the Spirit;
[7] and, for this reason David prayed, "Take not thy Holy Spirit from me."
[8] As it is his office to change the soul, and from a state of death in trespasses and sins, bring it into a new life, so it is his office to change our vile body, and fashion it like the glorious body of Christ: "He that raised up Jesus from the dead, shall also quicken your mortal bodies by his Spirit that dwelleth in you."
[9] As both body and spirit are redeemed by Christ, so both body and spirit are changed by the Holy spirit, and fitted for the presence and enjoyment of God.
The Holy Spirit is the Comforter of God's people. By his teaching, the knowledge of salvation by the remission of sins is obtained. The Saviour promised: "He shall take of mine, and shall show it unto you."
[10] In fulfilment of this promise, the Spirit makes known the sufficiency and suitableness of Christ as Saviour, and the efficacy of his blood to cleanse from sin. By the Holy Spirit the promises of the divine word are applied to the heart. Hence, peace and joy are called the fruit of the Spirit.
[11] These spiritual enjoyments, which are a foretaste of heaven, are called "the earnest of the Spirit."
[12] And, as the earnest is given by him, we have reason to conclude that the full possession will be given by him. As Christ will be the medium through which the felicity of the future world will be bestowed; so, the Holy Spirit will be the immediate agent in bestowing it. The first comfort here below, and the full bliss and glory of heaven, are alike his work.
[1] Ps. li. 10-12; Ezek. xxxvi. 27; John xiv. 26; Acts ix. 31; Rom. v. 5; viii. 13, 16, 26; 1 Cor. vi. 11; 2 Cor. i. 22; iii. 18; Gal. v. 22; 2 Thes. ii. 13.
[2] 1 Pet. i. 2.
[3] 1 Cor. vi. 11.
[4] John iii. 6.
[5]Gal. v. 25.
[6] Gal. v. 18.
[7] Eph. v. 18.
[8] Ps. li. 11.
[9] Rom. viii. 11.
[10] John xvi. 15.
[11] Gal. v. 22.
[12] Eph i. 13, 14; 2 Cor. i. 22.
John L. Dagg, Manual of Theology, Book Sixth, Doctrine Concerning the Holy Spirit, Chapter III, Office of the Holy Spirit
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While the word was in the process of being written, we see the Holy Spirit working apart from that written word. Especially in the Old Testament.
But...there was one major difference between the operation of the Holy Spirit in the Old Testament and the New Testament.
In the Old Testament, the Holy Spirit was not given to permanently indwell like in the New.
So again, your argument falls apart.
God Bless
Till all are one.