John the Baptist was really surprised when Jesus came to him to be baptized, but Jesus’ reply in Matthew 3:15 was: “it is proper for us to do this to fulfill all righteousness.”
But why was Jesus being baptized in John’s water baptism so necessary in fulfilling all righteousness? John’s baptism was all about “confessing sin” (verse 6), and “producing fruits in keeping with repentance” (verse 8), neither of which Jesus needed to do. Jesus didn’t need to confess to, or repent of, anything. But the Jews of that day, or Israel as a whole, did. They were the ones in desperate need of confessing their sins and producing fruits in keeping with repentance, because they had fallen far short of what God had called them to be and do.
God’s purpose for Israel had been clearly stated back In Isaiah 49:3, that “You are my servant, Israel, in whom I will display my splendour.” And in verse 6, “I will also make you a light for the Gentiles, that you may bring my salvation to the ends of the earth.” Unfortunately, Israel had failed miserably in fulfilling those two purposes, and God had punished them severely for it, by sentencing them to many years in slavery to pagan nations. And.even after they’d been freed from captivity in Babylon, they were still under the thumb of the Romans 400 years later in Jesus’ day.
But God had sent Jesus to change all that. To prepare Israel for Jesus’ coming, God sent John the Baptist in advance, telling the Jews in Matthew 3:1-3 to “Repent, for the kingdom of heaven is near” – taking a quote right out of Isaiah again, about “A voice of one calling in the desert, ‘Prepare the way for the Lord, make straight paths for him'” in Isaiah 40:3. It resulted in Jews “from Jerusalem and all Judea and the whole region of the Jordan” going to John to “Confess their sins,” verses 5-6, and be baptized by John in the Jordan river.
And John baptized them “with water for repentance,” verse 11, but that wasn’t enough to make up for Israel’s failure in fulfilling God’s purpose for them. Their baptism in water was only preparation for the one who could make up for it, the one coming after John who would “baptize” them “with the Holy Spirit,” verse 11.
But before Jesus could baptize those Jews with the Holy Spirit, God needed Jesus himself to be baptized in water too. Not for his own sake, but for Israel’s sake. The Israelites had clearly proved throughout their history that they could not confess their sins or produce fruits for repentance sufficiently enough to make up for all their failures. Their baptism in water, therefore, was only pointing them to the one who could. Only Jesus in his baptism could “fulfill all the righteousness” of confession and repentance they had been unable to fulfill themselves. His baptism could, and would, do that, not theirs.
The message was clear, that only in Jesus could true confession and repentance be made, sufficient enough to take away the sins of Israel. He was doing it for them, in other words, because only he could. But this would be the great beginning of God “bringing back those of Israel I have kept” and “restoring the tribes of Jacob,” in their mission of being “a light to the Gentiles” and bringing “God’s salvation to the ends of the earth” (Isaiah 49:6 again).
Or as Peter phrased it in Acts 3:26, “When God raised up his servant (Jesus), he sent him first to you (Jews) to bless you by turning each of you from your wicked ways.” And that “turning from their wicked ways” began with Jesus’ baptism fulfilling the confession and repentance the Jews and Israel had been unable to do themselves. But with that righteousness now fulfilled by Jesus, salvation from sins could now spread from the Jews to the Gentiles too, thereby fulfilling John the Baptist’s statement in John 1:29, “Look, the Lamb of God, who takes away the sin of the (whole) world.” That righteousness would now be fulfilled in Jesus too, all pictured so perfectly by his baptism.