“But when the Helper comes, whom I shall send to you from the Father, the Spirit of truth who proceeds from the Father, He will testify of Me.” (John 15:26)

Today’s big question: why is the Trinity important?

The Trinity is the doctrine that states there is one God but three Persons—God the Father, God the Son, and God the Holy Spirit. Scripture clearly states that there is one God yet three separate Persons (for example, see Matthew 28:19 and Mark 12:29). As we have discussed in the last three devotional series, each Person of the Trinity plays a role in salvation. Studying these roles in light of the doctrine of the Trinity gives us a deeper understanding of God and His Word.

Today’s passage references all three Persons and states that the Father and the Son will send the Holy Spirit to testify of Jesus. God’s only Son, Jesus, was sent into this world “that whoever believes in Him should not perish but have everlasting life. For God did not send His Son into the world to condemn the world, but that the world through Him might be saved” (John 3:16–17). The Holy Spirit testifies that Jesus is the Christ—the Messiah and Savior.

When we interpret this passage, we should recognize that each member of the Trinity is God. All three speak with authority because God—the Creator of everything—is our ultimate authority is every area, and that is the major reason why the Holy Spirit can testify of Jesus:

But God has revealed them to us through His Spirit. For the Spirit searches all things, yes, the deep things of God. (1 Corinthians 2:10)

If the Holy Spirit is not God, then we cannot completely trust the truths to which He guides us, such as Jesus being the Messiah.

God has given us this truth through His Word, and the Trinity is important simply because the doctrine is revealed in Scripture. Also, doctrine of the Trinity goes hand in hand with the doctrine of salvation (e.g., the many things that Jesus said and did have no meaning if He is not God). Even though the word “Trinity” is not found in Scripture, the doctrine is clearly presented.  http://www.answersingenesis.org/articles/2010/10/13/why-is-the-trinity-important