The Greek term used here, paraklētos, refers to a legal assistant in a court who pleads someone’s case before the judge (compare 1 John 2:1).

When on earth, Jesus was the means for believers to interact with God the Father since their sin prevented them from doing so directly. The Spirit is sent to do the same work. This is one of His many tasks. Paraklētos is used throughout Greek literature in a legal context

Finding an appropriate English translation for παράκλητος is a very difficult task. No single English word has exactly the same range of meaning as the Greek word. “Comforter,” used by some of the older English versions, appears to be as old as Wycliffe. But today it suggests a quilt or a sympathetic mourner at a funeral. “Counselor” is adequate, but too broad, in contexts like “marriage counselor” or “camp counselor.” “Helper” or “Assistant” could also be used, but could suggest a subordinate rank. “Advocate,” the word chosen for this translation, has more forensic overtones than the Greek word does, although in John 16:5–11 a forensic context is certainly present

“will teach you all things” This must be qualified. The Spirit does not teach believers in all areas of knowledge but about spiritual truth, especially in relation to Jesus’ person and work, the gospel.

a. παράκλητος (LN 12.19) (BAGD p. 618): ‘Helper’ [BAGD, LN, NTC; NASB, NCV, TEV], ‘Advocate’ [NICNT2; NET, NLT, NRSV], ‘advocate’ [REB], ‘Counselor’ [HTC; NIV], ‘Comforter’ [KJV], ‘support’ [Gdt], ‘Encourager’ [LN], ‘Mediator’ [BAGD, LN], ‘Paraclete’ [AB, WBC; NJB], ‘one who appears in another’s behalf, intercessor’ [BAGD]. This noun is also translated as a clause: ‘the Holy Spirit will come and help you’ [CEV], ‘the one who is coming to stand by you’ [Ph]. See this word also at 14:16.

John’s purpose in including this theme and this verse is not to explain how readers at the end of the first century may be taught by the Spirit, but to explain to readers at the end of the first century how the first witnesses, the first disciples, came to an accurate and full understanding of the truth of Jesus Christ. The Spirit’s ministry in this respect was not to bring qualitatively new revelation, but to complete, to fill out, the revelation brought by Jesus himself.

The role of the Spirit in this context is spelled out as that of instructor/teacher but clearly not in the sense of a replacement for Jesus.

The role of the Counsellor emphasized here is teaching. He will teach the disciples ‘all things’. ‘All things’ does not mean everything that it is possible to know, but all that Jesus himself taught them: he ‘will remind you of everything I have said to you’.

This promise is very important for today because it provides assurance from the Lord himself that the first witnesses, whose testimony is preserved in the New Testament, would be instructed by the Spirit regarding the truths that Jesus taught them, even though at the time he taught them they often did not understand

Everything stands in contrast to this (literally “these things”) of verse 25, and is best understood in light of 16:13. That is, the Helper will enable the disciples to understand the full implications of Jesus’ words. Everything (in the context of will teach you everything) may seem too inclusive. The Implication is simply “teach you everything you need to know about what I have said.”

Shall teach you all things (ὑμας διδαξει παντα [humas didaxei panta]). The Holy Spirit knows “the deep things of God” (1 Cor. 2:10) and he is our Teacher in the Dispensation of the Holy Spirit of both new truth (verse 25) and old

The Spirit, as God’s means of communication on earth, instructs believers and leads them to follow God’s will. The Spirit gives them access to God, His plans, and His wisdom. He can do so because of Jesus’ sacrifice for sins.

Why, the Spirit shall teach them, shall be their standing tutor. He shall teach them all things necessary for them either to learn themselves, or to teach others. For those that would teach the things of God must first themselves be taught of God; this is the Spirit’s work.

They would need further instruction, and this the Holy Spirit would give to them. The Spirit of God knows the “things of God” and “searcheth all things, year, the deep things of God” (1 Cor. 2:10, 11), and He is able to impart them to men who are willing to be instructed.

The first half of the promise, “He will teach you all things,” is directed solely to the apostles. The Spirit not only brought to their remembrance exactly what Jesus said (v 26b), but He also taught them what Jesus had meant

shall teach you all things] i.e. ‘guide you into all the truth’ (16:13). He shall teach them the Divine truth in its fulness; all those things which they ‘cannot bear now,’ and also ‘things to come.’

The Spirit would lead the disciples into further truth after Jesus was gone, but it would be based on what they already knew about Him and had learned from Him.

This is the second side of the work of the Spirit, who not only was to reveal what was new, but was to recall to the memory of the apostles the old truths that Jesus had taught.

One of the Spirit’s principal tasks, after Jesus is glorified, is to remind the disciples of Jesus’ teaching and thus, in the new situation after the resurrection, to help them grasp its significance and thus to teach them what it meant.

Instead, the Spirit’s role is more like that of a prompter, or one who brings to memory the ideas of Jesus that one should be able to recall.

This role of prompter/teacher is crucial for John because the task of the Holy Spirit could be said to be one of confirming and interpreting the message proclaimed and demonstrated by Jesus.

Make … remember is also used in Luke 22:61 where Peter recalls Jesus’ words. It is best to take these two phrases (teach you everything and make you remember all that I have told you) as synonymous, the one reinforcing the other. The method by which the Spirit teaches the disciples everything is by “making them remember” all that Jesus has taught them, and by bringing out the implications of his teaching.

When asked to give a reason for the hope that is in them (1 Peter 3:15), Christians who have been diligent students of the Bible may have the confidence that the Holy Spirit will call to mind passages suited to the occasion.

He also will help the Apostles remember all the things Jesus had said to them and clarify their meaning so that they can record them in the Scriptures.

The second half of the promise, “He will … bring to your remembrance all things that I said to you,” is also only directed to the apostles. In their writing of the NT they were enabled by the Holy Spirit to remember precisely what Jesus had said. This is one of the most important verses in the NT concerning biblical inspiration and inerrancy.

bring all things to your remembrance] Not merely the words of Christ, a particular in which this Gospel is a striking fulfilment of this promise, but also the meaning of them, which the Apostles often failed to see at the time: comp. 2:22, 12:16; Luke 9:45, 18:34, 24:8. “It is on the fulfilment of this promise to the Apostles, that their sufficiency as Witnesses of all that the Lord did and taught, and consequently the authenticity of the Gospel narrative, is grounded” (Alford).

But notice how he promises the Spirit will teach. He says the Spirit will suggest or remind. Therefore, the Spirit will not be a maker of new revelations.