Why can’t the Holy Spirit if “He” is God speak of his own initiative? Why is it that “He” can only speak what “He” hears?
In his gospel, John records Jesus talking about the Holy Spirit as he was preparing to leave the disciples, go to the cross, and then to heaven in the Olivet Discourse of John 13-17. The Holy Spirit is one of the main subjects of the passage.
One example of what you are referring to is “He will not speak on His own initiative, but whatever He hears, He will speak” (John 16:13, NASB). When we look at the context of this passage, we can begin to understand why it says this about the Holy Spirit.
Other translations, like the ESV, help us to understand the context a little bit better. It talks about the authority of the Holy Spirit as coming from Jesus, whom the disciples already know. If we quote the whole verse,
“When the Spirit of truth comes, he will guide you into all the truth, for he will not speak on his own authority, but whatever he hears he will speak, and he will declare to you the things that are to come.”John 16:13, ESV
Jesus has already told the disciples that the Holy Spirit will come after he leaves. The Holy Spirit will take over Jesus’ ministry, dwelling in the disciples to guide them into all truth. Then as he guides them, he will not lead them astray.
The Holy Spirit will speak what he hears, and what he hears comes from Jesus. Take a look at the next verse:
“He will glorify me, for he will take what is mine and declare it to you.”John 16:14, ESV
So everything the Holy Spirit says in regard to truth and guiding the disciples is based off of what Jesus has already done and said in his own ministry. The Holy Spirit’s goal is not to forge his own new path in us. It is to glorify Jesus and all that he tells us.
What he hears is from Jesus. It’s not from some other place. We can trust the Holy Spirit when he speaks to us. He declares what Jesus declares to us. This can be an allusion to the doctrine of illumination, that the Holy Spirit speaks through Scripture directly to us, bringing up our own circumstances as we read the Scriptures.
He applies Scripture directly to us as we read. Since the Scriptures come from God, he helps us to understand them. This may at least be in part what Jesus is saying here. Either way, what Jesus speaks, the Holy Spirit hears and speaks to us. He is the Liaison between Jesus and believers in them.
The Holy Spirit can indeed speak for himself. He often does. Jesus was teaching the disciples that when the Holy Spirit speaks, he speaks with the authority of Jesus. It is not that he does not stand on his own as one of the three Persons of the Trinity.
In this context, the Holy Spirit was glorifying Jesus, the Son of God. As Jesus introduces the disciples to the Holy Spirit who will be their Helper and Comforter when he has gone, Jesus introduces him as the one to replace him in his physical presence with them.
They need to be able to trust the Holy Spirit and to know that he is connected with Jesus. So this is how Jesus begins the explanation of who he is and what he does. I don’t know what you’ve been taught about Christian theology, but your question seems to iterate that you do not believe the Holy Spirit is his own individual Person as part of the Trinity.
It has been affirmed throughout Scripture that the Holy Spirit is his own Person. There is ample evidence throughout especially the New Testament to show that he stands alone as his own Person. But he also works together with the other members of the Trinity, the Father and Jesus the Son.
Just because Jesus introduces the Holy Spirit to the disciples and to us in familiar terms based on him and his own ministry does not mean that the Holy Spirit must only do what Jesus says. He has his own abilities and mind. He is in agreement with Jesus and the Father. But he can express himself in his own ways.
Be careful not to think that the Holy Spirit is some kind of force or thing. The Holy Spirit Is a Person and we must be careful not to grieve him by thinking he is anything but his own Person. If we go back one verse from where we started, John 16:12, Jesus tells the disciples he has many things to tell them, but they can’t handle it right now.
In this context, the Holy Spirit is the one to reveal to them what Jesus does not either have time to tell them at this moment in human history, or that they cannot handle to hear from him because of the situation of his leaving. The disciples didn’t take Jesus’ announcement that he was going away from them well in John 14.
Perhaps because of their emotional state, Jesus must speak through the Holy Spirit to them later, when they are able to take in everything else he wants to tell them. So the Holy Spirit takes his place in them so that they can understand everything that he wants to tell them.
The Holy Spirit still speaks today to Christians when we’re open to listening to what he says. He guides us today to be like Jesus. One of his chief jobs is to lead us into the holiness of Christ, to conform us to Jesus’ image (Romans 8:29).
We know that we can trust the Holy Spirit because he is the Spirit of Truth. He guides us into the same truth that Jesus was guiding the disciples into when he spoke to them in the New Testament. The Holy Spirit uses the Scriptures of the New Testament, and the Old Testament as well, to lead us wherever God wants us to go.