This is the message we have heard from him and proclaim to you, that God is light, and in him is no darkness at all.  [6] If we say we have fellowship with him while we walk in darkness, we lie and do not practice the truth.  [7] But if we walk in the light, as he is in the light, we have fellowship with one another, and the blood of Jesus his Son cleanses us from all sin.  [8] If we say we have no sin, we deceive ourselves, and the truth is not in us.  [9] If we confess our sins, he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness.  [10] If we say we have not sinned, we make him a liar, and his word is not in us. 1 John 1:5-10 (ESV) 

Do you practice the truth?  How can you practice it if you don’t know what it is?  Do you know what it is?    What is it?  Did you know that it is the very first piece of armor that the Christian dons in order to prevail in the warfare of this world?  How do you put it on?

Jesus himself said, “I am the way, the truth, and the life.”  John says, “In the beginning was the Word, and the Word was with God, and the Word was God.  [2] He was in the beginning with God.  [3] All things were made through him, and without him was not any thing made that was made.  [4] In him was life, and the life was the light of men.  [5] The light shines in the darkness, and the darkness has not overcome it …  And the Word became flesh and dwelt among us, and we have seen his glory, glory as of the only Son from the Father, full of grace and truth … [16] And from his fullness we have all received, grace upon grace.  [17] For the law was given through Moses; grace and truth came through Jesus Christ.   John 1:1-5, 14, 16, 17 (ESV) 

So, we put on truth by “putting on” Christ.  How?  By getting to know him, intimately.  By reading, remembering, and living his Word, for he is the Word made flesh.  Remember Psalm 119:160 which says, “The sum of your word is truth, and every one of your righteous rules endures forever.”

Notice that “the sum” of Christ’s Word is truth.  This means we must “add it all up” to get the truth.  We do not have the truth when we take a verse here or a verse there and make a doctrine out of it.  We only arrive at truth when we take “the sum” of Christ’s words, which is the entire Bible, for all Scripture is “God-breathed.”

There are whole denominations, for example, which take the verse, “Baptism, which corresponds to this, now saves you, not as a removal of dirt from the body but as an appeal to God for a good conscience, through the resurrection of Jesus Christ”  1 Peter 3:21 (ESV)  and argue that a person must be baptized by being immersed in water in order to be saved from hell.   This verse has nothing to do with initial faith in Jesus and the cognizance of spiritual salvation that that faith brings.  It deals with an entirely different kind of salvation, the salvation of the soul, the salvation that Paul said must be worked out with fear and trembling.  Peter here speaks of the “washing of water with the word” that Paul talks about in Ephesians 5:26.  From taking all of Christ’s words we learn that we must continually wash, or cleanse, ourselves by the Word of God in order to be set apart and useful for God’s work.  This is what Peter is talking about; it has nothing to do with initially “getting saved!”

So, we find that we “practice the truth” when we: 1) diligently get to know that truth by studying God’s Word and 2) determine that we ought to do what that truth says we ought to do.  Otherwise, we remain merely hypocrites who say one thing and do another.  Further, John tells us, If we confess our sins, he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness.  So, we see that to practice the truth means, in essence, to practice righteousness.  If we do not practice the truth, then we walk in darkness and his Word is not in us.