John 3:31-end

Some translations have these words as the words of John the Baptist, others as the words of John the disciple whom Jesus loved. It all depends on the quotation marks! But I am sure that the two John's would have both agreed with these words.
The words testify to Jesus as the One from "above" (as in John 3:7 - you must be born "from above" rather than "again" as Nicodemus misunderstands"!!), the One from Heaven. The One from Heaven has been given words to say - words that are inspired by the Holy Spirit which has been given without limit. The words and the power of God given through the Holy Spirit are the true nature of God - we know what God is like because of His Word in Christ. A person who hears and accepts this - i.e. believes in the nature of God and aligns their lives to the will revealed (however difficult and flaky this adjustment may be) is heading for eternity with God.
What is unusual is the understanding that for those who hear and reject God's word, "God's wrath remains on him". To understand "wrath" in the context of this heavenly language is to draw us back to the reality of a world in which people are evil and aggressive. Many will hear the words of Jesus and see his life as weakness and foolishness. They will not allow their grip on what they want to relax whatever the cost especially to others. The reality of wickedness in humanity when this happens is too real. This cannot be a situation that God will allow to continue for ever. So the wrath of God - although forgiveness, love and the Spirit are offered without limit - remains inevitable for those who continue to reject the way of peace.