In the Gospel according to John, John the Baptist is always called just plain ‘John’. That’s surprising. Why not distinguish more clearly between John the Evangelist and John the Baptist?
The answer is: their main role is in fact the same. They both testify to Jesus. The Baptist does of course baptise, but his great task in the Fourth Gospel is actually to bear witness. We are first introduced to him with the words ‘He came as a witness to testify concerning that light’ (1:7), and the Gospel sums up his ministry by speaking of people accepting his testimony about Jesus (10:41).
John’s testimony comes in two stages. First of all he says that someone greater is coming (1:15). Then he goes much further, identifying Jesus as the ‘the Lamb of God who takes away the sin of the world’ (1:29). How does he already know by chapter 1 that Jesus is the Lamb of God?
John explains that he had been told: ‘The man on whom you see the Spirit come down and remain is the one who will baptise with the Holy Spirit’ (1:33). This allowed him to point out ‘the Chosen One’ (1:34). But how did John get from God’s revelation of Jesus as ‘the one who will baptise with the Holy Spirit’ to his witness to Jesus as ‘the Lamb of God who takes away the sin of the world!’? John himself received prophetic insight which allowed him to identify the Spirit-baptiser. But it seems that he was also a careful reader of Old Testament prophecy, particularly the latter part of the book of Isaiah. After all, that same part of Scripture provided John’s job description as ‘the voice of one calling in the wilderness, “Make straight the way for the Lord’’ ’(1:23, quoting Isa. 40:3).
John the student of Isaiah
From Isaiah, John could learn about God’s Chosen One, the servant on whom God’s Spirit rests (42:1 and 61:1) and who fulfils the royal task of bringing justice to the nations (42:1, 4) as well as to Zion (61:1–3). John could learn that the promise of God’s outpouring of His Spirit (44:3) is connected to God’s servant because the Sovereign Lord sends His Spirit along with Him (48:16). John must have connected the dots and come to see that the Messiah and the servant are the same person: the Messiah who brings salvation is also the servant who delivers His people from the exile of sin as the lamb that bears the sins of many sheep (53:4-12).
So it was very likely Isaiah that helped John move from ‘the one who will baptise with the Holy Spirit’ to ‘the Lamb of God who takes away the sin of the world!’ John bears fuller testimony to the true light by being attentive to Isaiah’s testimony to the light (e.g. Isa. 2:5; 9:2; 42:6; 49:6; 51:4). Indeed this light is the glory of God, even God Himself (60:1,19-20). So the one on whom God’s Spirit rests had to be the one through whom God’s Spirit would be poured out on God’s people. And this had to be the one who would deal with the roadblock that is sin. The Anointed One is indeed the Lamb of God that takes away the sin of the world. It was the book of Isaiah that helped John make sense of all that he was seeing in Jesus, so he could say much more about Jesus than the one thing that had been specifically revealed to him.
If John the Baptist did not merely reproduce words given to him, but added depth by connecting different parts of Scripture, how much more should we who are not given specific divine revelation be encouraged to draw out the full message of God’s revelation by reading each part in the light of other parts?
