Essentially the opposite of this question:
What is the earliest recorded post-NT instance of a clear and unambiguous denial of the personhood of the Holy Spirit? When was it claimed for the first time that the Holy Spirit is not a Person, distinct from the Father and the Son, in the history of Christianity?
When did this belief reach widespread acceptance among Christians for the first time, if ever?
The idea that when the Christian Greek scriptures speak of the Holy Spirit, it is not speaking of a person, but of an impersonal force, or power, stems from outside the first-century Church. Hellenistic philosophy at the time around and after the New Testament writings were completed (which is usually held to be just before the start of the second century A.D.) seems to be the earliest grounds for denial. Here is what this theologian writes about the Hebrew word ruach, and the Greek word pneuma (spirit) in the Bible:
"[they] are onomatopoeic terms, both their physical formation and their sound conveying a sense of their basic meaning: the expulsion of wind or breath, the idea of air in motion. 'Spirit' expresses, in its most fundamental form ('the breath of life'), power, energy and life.
In the world of Hellenistic philosophy, which provided the wider intellectual environment of the later biblical period, pneuma was thought of as a kind of deeply refined and purified matter (matter itself being thought of as fallen and evil by definition). In the philosophy of the Stoics, for example, it was thought of as the stuff of the soul, a kind of 'vital nervous fluid' which extends from the soul throughout the person, endowing him or her with energy and life. [3] The Holy Spirit, Sinclair Ferguson, p. 16 (I.V.P. 1996)
As the New Testament itself describes the Holy Spirit as that which one can lie to (and so be struck dead as having lied to God - Acts 5:1-11), personhood was attributed. Personhood cannot be attributed to matter.
Personhood became clear once the Holy Spirit was given / bestowed upon Christians after Jesus returned to heaven and sent the Holy Spirit as he had promised to do. Yet any Christians in following centuries who became influenced by Hellenistic philosophy, and Gnosticism, regarding 'spirit', would corrupt Church teaching as to the Spirit's personhood in Christianity. This is not a clear and unambiguous answer, which may be why three years have passed without anyone answering. It would be astonishing if a time and date could be identified, with accurate quotes from accredited ancient Church writings. But I hope someone can do that!
[3] E. DeWitt Burton, Spirit, Soul and Flesh (Chicago, IL: University of Chicago Press, 1918) p. 113. Cf. G.L. Prestige, God in Patristic Thought (London SPCK, 1952), pp. 17ff.
I take it here you are asking for a denial of 'personhood', not equal personhood?- Yes, that's what I mean. Denial of personhood regardless of whether equality is affirmed or denied.