Where we can find that verse that both the Father and Holy Spirit witness to Jesus?
((Witnessing REQUIRES distinct persons)) So you are saying to distinct spirits witnessing?
Distinct persons witness.
Whether they are spirit or not is irrelevant.
At the baptism of Jesus, the Father witnessed to Jesus with his voice.
At the same event, the Holy Spirit witnessed to Jesus by the dove resting on his head.
By the way, this is another set of verses that the Oneness advocate has issues with explaining, because the Father, Son, and Holy Spirit are present at the same time.
Additionally, according to these verses, the Father bore witness to Jesus, along with John the Baptist. This proves the distinction of Persons between the Father and Son (again), because the same person cannot bear witness to himself, and claim that it is a witness.
John 5:30-47 30 “I can do nothing on my own. As I hear, I judge, and my judgment is just, because I seek not my own will but the will of him who sent me
. 31 If I alone bear witness about myself, my testimony is not true. 32 There is another who bears witness about me, and I know that the testimony that he bears about me is true. 33 You sent to John, and he has borne witness to the truth. 34 Not that the testimony that I receive is from man, but I say these things so that you may be saved. 35 He was a burning and shining lamp, and you were willing to rejoice for a while in his light. 36 But the testimony that I have is greater than that of John. For the works that the Father has given me to accomplish, the very works that I am doing, bear witness about me that the Father has sent me.
37 And the Father who sent me has himself borne witness about me. His voice you have never heard, his form you have never seen, 38 and you do not have his word abiding in you, for you do not believe the one whom he has sent. 39 You search the Scriptures because you think that in them you have eternal life; and it is they that bear witness about me, 40 yet you refuse to come to me that you may have life. 41 I do not receive glory from people. 42 But I know that you do not have the love of God within you.
43 I have come in my Father's name, and you do not receive me. If another comes in his own name, you will receive him. 44 How can you believe, when you receive glory from one another and do not seek the glory that comes from the only God? 45 Do not think that I will accuse you to the Father. There is one who accuses you: Moses, on whom you have set your hope. 46 For if you believed Moses, you would believe me; for he wrote of me. 47 But if you do not believe his writings, how will you believe my words?”
As I have said, Oneness theology is plainly unbiblical, because interpersonal activity between the Father, Son, and Holy Spirit is unintelligible if their theology is true. The Trinity doctrine is the only one that makes sense of Scripture.
Of course, heretics of all types will continue to plague the church with their denial of this. And, uneducated people will continue to perpetuate their falsehoods.