Dougan Clark preaches about the Holy Spirit as a distinct person within the Trinity, emphasizing His deity, personality, and role in the Godhead. The sermon highlights the Holy Spirit's involvement in inspiring the Bible, guiding the early Church, and working alongside the Father and the Son in the salvation plan. Clark addresses the importance of reverent worship and proper terminology when referring to the Holy Spirit, distinguishing His unique attributes from those of Christ and God.

I say who, not what, and by this mode of expression it may be understood at the outset that I am inquiring about a person—not a thing. The Holy Spirit is not an influence, nor an attribute, nor an emanation, but a person. He is not merely a messenger proceeding from the Father and the Son, but one and co-eternal with the Father and the Son. He is not simply, as the etymology of the word spirit might imply, the breath of God, nor the abstract power of God, nor the life of God, nor the life of Christ—but God Himself. The Saviour uniformly uses the personal pronouns, he, him, whom, himself, in designating the Comforter or the Spirit of Truth, and although there are two or three passages in the English New Testament, in which the neuter forms, itself and it, are employed in reference to the Spirit, yet everywhere in the Bible His personality is recognized and His Godhead asserted. “Why,” said Peter to Ananias, “hath Satan filled thine heart to lie to the Holy Ghost? thou hast not lied unto men but unto God. “Whereof,” writes the author of the Epistle to the Hebrews, “the Holy Ghost also is a witness to us; for after that He had said before, ‘This is the covenant that I will make with them after those days saith the Lord.’” In the former of these quotations the terms, “Holy Ghost,” and “God,” in the latter the terms, “Holy Ghost,” and “the Lord,” are evidently used interchangeably to designate the same Almighty Being. And as the Holy Ghost is one with God the Father, He is also one with God the Son. In direct connection with the promise of the Comforter, the Saviour said to His mourning disciples, “I will not leave you comfortless, I will come to you;” and His final parting words to them before His ascension were, “Lo I am with you alway, even unto the end of the world.” The Holy Ghost is called Spirit of God, Spirit of Christ, and Christ. He inspired the writers of the Bible. He said to the Church at Antioch, “Separate me Barnabas and Saul, for the work whereunto I have called them.” He forbad Paul to preach the gospel in Asia, and suffered him not to go into Bithynia. He determined for, and with, the first council at Jerusalem, what restrictions should be imposed on the Gentile converts. He is associated with the Father and the Son in the final commission to the disciples, “Go ye therefore and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost;” and the attributes of Deity, eternal existence, omniscience, omnipotence, omnipresence, creative power, are all ascribed to Him. And here I will venture to ask one or two questions. (1). Is not the practice of designating the Holy Ghost by the impersonal pronoun it, and praying for its influence and its work in our hearts, calculated to detract somewhat from that worshipful reverence which is due to His dignity, personality, and deity? (2). Is it not better to apply to this divine Being, some one of the appellations used in Scripture, such as, Holy Ghost, Holy Spirit, Comforter, or Spirit of Christ, than to employ instead the name of one of His attributes or workings, as “the light,” “the truth,” “the seed,” or the “inward voice”? It would certainly seem to me, less ambiguous and more in accordance with the form of sound words, not to designate the Holy Ghost by any term which in the Bible is applied only to Christ or to God. The Spirit is truth, but Christ is the truth the Spirit quickens the dead soul into life, but Christ is the life—the Spirit points the way, but Christ is the way—the Spirit makes manifest, and “whatsoever doth make manifest is light,” but God is light, and Christ is the light of the world—the Spirit begets love in the soul, but God is love—the Spirit testifies of the “seed of the woman” which shall bruise the serpent’s head, and that “incorruptible seed” is Christ Himself. The mystery of the Godhead will ever be incomprehensible to the finite mind. In approaching that “holy ground” we need to tread reverently and with uncovered feet. No fact is more clearly set forth in the Holy Scriptures than that God is one, and yet He has condescended to reveal Himself in the threefold character of Father, Son, and Holy Ghost. And as in the wondrous plan of salvation, the Son performs certain definite offices distinct from those of the Father, so the Holy Spirit also accomplishes a work peculiarly His own. It is to a consideration of the offices of the Spirit, that the following pages will be principally devoted. Note - I take pleasure in acknowledging my indebtedness for some of the thoughts in this chapter to an excellent treatise on the offices of Christ, entitled “The Morning Star,” by my beloved friend and fellow-laborer in the gospel, Luke Woodard, of Newgarden, Indiana, U.S.A.