I have still many things to say to you, but you are not able to bear them or to take them upon you or to grasp them now. 13 But when He, the Spirit of Truth (the Truth-giving Spirit) comes, He will guide you into all the Truth (the whole, full Truth). For He will not speak His own message [on His own authority]; but He will tell whatever He hears [from the Father; He will give the message that has been given to Him], and He will announce and declare to you the things that are to come [that will happen in the future]. 14 He will honor and glorify Me, because He will take of (receive, draw upon) what is Mine and will reveal (declare, disclose, transmit) it to you. 15 Everything that the Father has is Mine. That is what I meant when I said that He [the Spirit] will take the things that are Mine and will reveal (declare, disclose, transmit) it to you. John 16:12-15 AMP
The Holy Spirit is the Spirit of Truth – He will always speak the Truth and lead you into the Truth. He does not bring you His own message or His own opinion. He will never speak anything contrary to the Word of God. Everything He says is of God and from God. He never speaks on His own authority – He only speaks on the authority that He has been given by Jesus and by the Father. He tells us whatever He hears the Father say – He gives the message that has been given to Him. He is the One Who announces and declares the things that are to come.
The Holy Spirit takes, receives, and draws upon that which belongs to Jesus and which comes from Him and He reveals it to us. Therefore and thereby, He honors and glorifies Jesus! He brings glory to Jesus, because He speaks only the words that come from Jesus. He brings glory to the Father, because He speaks only the words that come from the Father. Obviously, then if we or anybody else speaks words that do not come from the Father, Son or the Holy Spirit – words spoken on our own authority, by our own opinion, and coming from our own heart and mind – then they are not the truth and they will not bring glory to the Lord.
Anyone who rejects Me and persistently sets Me at naught, refusing to accept My teachings, has his judge [however]; for the [very] message that I have spoken will itself judge and convict him at the last day. 49 This is because I have never spoken on My own authority or of My own accord or as self-appointed, but the Father Who sent Me has Himself given Me orders [concerning] what to say and what to tell. 50 And I know that His commandment is (means) eternal life. So whatever I speak, I am saying [exactly] what My Father has told Me to say and in accordance with His instructions. John 12:48-50 AMP
Jesus, Himself did not speak on His own authority or of His own accord – He only said what His Father told Him to say. Therefore, everyone who hears Him is accountable before God to receive it as the Truth and be saved or to reject it and be judged. If Jesus did not speak on His own authority and the Holy Spirit does not speak on His own authority, then we certainly have no right to say or preach anything that has not been given to us by the Father. We have no right to preach our opinions apart from the Word of God. We have an obligation to preach the Word as it is, with no changes, no compromise and no dilution.
And how from your childhood you have had a knowledge of and been acquainted with the sacred Writings, which are able to instruct you and give you the understanding for salvation which comes through faith in Christ Jesus [through the leaning of the entire human personality on God in Christ Jesus in absolute trust and confidence in His power, wisdom, and goodness]. 16 Every Scripture is God-breathed (given by His inspiration) and profitable for instruction, for reproof and conviction of sin, for correction of error and discipline in obedience, [and] for training in righteousness (in holy living, in conformity to God’s will in thought, purpose, and action), 17 So that the man of God may be complete and proficient, well fitted and thoroughly equipped for every good work. 2 Timothy 3:15-17 AMP
And we have the prophetic word [made] firmer still. You will do well to pay close attention to it as to a lamp shining in a dismal (squalid and dark) place, until the day breaks through [the gloom] and the Morning Star rises ( comes into being) in your hearts. 20[Yet] first [you must] understand this, that no prophecy of Scripture is [a matter] of any personal or private or special interpretation (loosening, solving). 21 For no prophecy ever originated because some man willed it [to do so–it never came by human impulse], but men spoke from God who were borne along (moved and impelled) by the Holy Spirit. 2 Peter 1:19-21 AMP
Whether you preach, pray or prophesy, let it be led, guided and guarded by the Holy Spirit. Bring glory to God as you speak only the words that He puts in your mouth.