“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)
On Pentecost, the Holy Spirit gave the disciples both boldness and wisdom so that they could go forth and preach the gospel as Jesus had commanded them. On the night of the Last Supper, this was what Jesus had promised them the Spirit would do. He would guide the disciples into all truth so that they could preach the gospel. Through their words and testimony, the Holy Spirit would convict sinners. he would show them the truth about their sins and lead them to repentance.
The Holy Spirit still manifests Himself in this way today. He empowers and enlighteners believers to preach the gospel in word and in deed. He convicts people of sin, points them to Jesus and guides those who respond into all truth. This truth is not scientific truth or medical truth or things that can be known from observing the world. This truth is not relative truth either, that is, it is not truth relative to the situation, the needs of the moment, the person or the culture.
The truth Jesus spoke of and which the Holy Spirit reveals is spiritual truth. The first truths He reveals concern the sinfulness of the human heart as well as the offer of God’s grace and mercy in Jesus. Then the truth He imparts tells us how we to interpret what we observe in the world and how we are to use that truth in a way that is pleasing to God. In addition the truth imparted by the Holy Spirit is truth about God, Jesus and His word, how we are to serve Him, how we are to look at life, how we are to live and how we are love one another with the sacrificial love that Christ has for us.