Practical consequences
He came as a witness, to bear witness about the light. (John 1: 7)
In the beginning was the Word, and the Word was with God, and the Word was God. He was in the beginning with God. All things were made through him, and without him was not any thing made that was made. In him was life, and the life was the light of men. The light shines in the darkness, and the darkness has not overcome it. There was a man sent from God, whose name was John. He came as a witness, to bear witness about the light, that all might believe through him. He was not the light, but came to bear witness about the light. The true light, which gives light to everyone, was coming into the world. He was in the world, and the world was made through him, yet the world did not know him. He came to his own, and his own people did not receive him. But to all who did receive him, who believed in his name, he gave the right to become children of God, who were born, not of blood nor of the will of the flesh nor of the will of man, but of God. 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. (John bore witness about him, and cried out, “This was he of whom I said, ‘He who comes after me ranks before me, because he was before me.’”) For from his fullness we have all received, grace upon grace. For the law was given through Moses; grace and truth came through Jesus Christ. No one has ever seen God; the only God, who is at the Father's side, he has made him known. (John 1: 1-18)
Jesus's precursor, St. John the Baptist, recognised Him because he allowed himself to be led by the Holy Spirit. Normally men judge others according to appearances. John the Baptist, however, witnessed that light always comes from God, while confusion and darkness, which do not permit us to distinguish good from evil and truth from falsity, come from the Evil One. This is why penance is so important, so that we can remove the darkness of sin from our heart to make room for God's light. Let us remember that St. John's preaching also applies to us today and may we draw practical consequences from it in our daily lives.
