In this passage John shows that he is NOTORIOUS upset or threatened by Jesus’ ministry, hrye is ecstatic about what is going on. He gives an analogy by comparing himself to the best man in a wedding. If you have ever had the privilege of being a best man, then you know exactly the point John the Baptist is making. The best man knows that the wedding has absolutely NOTHING to do with him. He is there to assist, rejoice and celebrate with the groom and his upcoming marriage.
Jesus is the bridegroom and the bride is the Church. The “friend of the bridegroom” is John the Baptist. John not only says he is joyful, but his joy is COMPLETE (A.K.A. he can die a happy man). John says in 3:30, “He must increase, but I must decrease.” John was not making a noteworthy quote he was declaring truth. According to author and theologian R.C. Sproul, “He (John) was called to go before Christ, and once he had announced Christ, then John was to go into the background that Christ might emerge in the fullness of His leadership as the appointed Messiah. ‘It is necessary,’ John said. ‘It’s not optional. This must happen. It must take place. I must decrease. He must increase.’” We all would do well if we lived by and believed this proclamation.
If you and I make it a point to promote Jesus and not promote ourselves then we would see increase. Our job in this world is to promote Jesus and not promotion of self. Verses 31 and 32 appear to be the reflective words of John “the Evangelist” (the author) and serve as an explanation as to why Jesus must increase, since he is from above, and ultimately above all. John the Baptist speaks of earthly things thus he does not have the same authority as Jesus, so it is imperative that Jesus increase and John decrease. Those who do receive Jesus’ testimony do so by accepting that his Word is indeed the Word of God and that God is the one true God. In closing John re-iterates the theme of this chapter: Jesus is the Son of God; all things are given to Him by the Father. Anyone who believes (Commits unto, trusts, places confidence in, has saving faith) in Jesus has eternal life. Whoever does not believe or does not obey will not have eternal life and will face the wrath of God.
 Sproul, R.C. (2009). St. Andrew’s Expositional Commentary: John p. 52 Lake Mary, FL., USA: Reformation Trust Publishing.