What does John 1:36 mean?

In verse 29, John the Baptist referred to Jesus as "The Lamb of God." This actually doesn't refer to a temple sacrifice, but to the days of Passover and Moses. The final plague of Egypt was the death of the firstborn, and only those whose doors were covered with the blood of a lamb were spared. The preparation for sudden travel, and the covering of blood, made a powerful symbol of Jesus' work on the cross. In fact, the instructions given to Moses would have created a bloody cross on every Israelite door, from the blood of that sacrificed lamb (Exodus 12:21–23). After the judgment, those who stepped through that door were free. This is a metaphor for salvation in Christ. Only those covered by the blood are spared from judgment; only by going through that door can a person be set free. This is a change in the Baptist's ministry. Up to this point, he had been telling people that the Messiah was coming. Now, he tells people that Messiah is here!