Spirit of truth
Literally, of the truth. See on John 14:7.
Will guide ( ὁδηγήσει )
From ὁδός , way, and ἡγέομαι , to lead. The kindred noun, ὁδηγός , guide, leader, occurs Matthew 15:14; Acts 1:16, etc.
Into all truth ( εἰς πᾶσαν τὴν ἀλήθειαν )
Rev., more correctly, into all the truth. Some editors read, ἐν τῇ ἀληθείᾳ πάσῃ , in all the truth. Others, εἰς τὴν ἀλήθειαν πᾶσαν , joining πᾶσαν in an adverbial sense with will guide you: i.e., will guide you wholly into the truth. The Spirit does not reveal all truth to men, but He leads them to the truth as it is in Christ.
Rev., rightly, from himself. See on John 7:17.
He shall hear ( ἂν ἀκούσῃ )
Some read, ἀκούει , heareth, and omit ἂν , the conditional particle. Ὅσα ἂν ἀκούσῃ , the reading of the Rec. Text, is, strictly, whatsoever things he may have heard.
Will shew ( ἀναγγελεῖ )
Better, as Rev., declare. Compare Mark 5:14, Mark 5:19; Acts 20:27; 2 Corinthians 7:7. Also to rehearse; Acts 14:27. Used of the formal proclamation of the Christian religion (Acts 20:20; 1 Peter 1:12; 1 John 1:5). See on Acts 19:18.
Things to come ( τὰ ἐρχόμενα )
The article, omitted by A.V., is important. The meaning is not, He will show you some things to come, but the things that are to come, or the things that are coming. These things are whatsoever He shall hear. The phrase occurs only here in the New Testament.