'Truth' in the Bible

This is the John who taught the truth concerning the Word of God and the truth told us by Jesus Christ-- a faithful account of what he had seen.

I John, your brother, and a sharer with you in the sorrows and Kingship and patient endurance of Jesus, found myself in the island of Patmos, on account of the Word of God and the truth told us by Jesus.

Then I fell down at his feet to worship him, but he [stopped me and] said to me, “You must not do that; I am a fellow servant with you and your brothers and sisters who have and hold the testimony of Jesus. Worship God [alone]. For the testimony of Jesus is the spirit of prophecy [His life and teaching are the heart of prophecy].”