The next day, he saw Jesus coming to him, and said, "Behold, the Lamb of God, who takes away the sin of the world!

 So the two disciples of John followed Jesus. It may well be that they were too shy to approach him directly and followed respectfully some distance behind. Then Jesus did something entirely characteristic. He turned and spoke to them. That is to say, he met them half way. He made things easier for them. He opened the door that they might come in. 