He starts to teach, and a crowd assembles. Not only is it the time of the feast, and Jerusalem is packed with visitors, but there is great messianic expectation about Jesus.
Their first question has a hint of contempt in it: “Where did this guy learn all this stuff? He didn’t study under the masters.” But they’re curious because Jesus uses methods of debate that are taught in the schools, and they know he hasn’t been educated by any of them. So they respect him, but they don’t.
Jesus makes it clear: “I didn’t study from the masters; everything I know I got from the Master Himself.” He denies being self-taught (well, he would have been immediately discredited if he said he had been), but says he got his material straight from God. Then he says, “Any of you who follow God’s will by choice will be able to tell that what I’m telling you is true.” Notice that choosing to do God’s will comes first, and then the confidence comes later.
Jesus continues: People who speak on their own usually do it bringing attention to themselves, but the one who brings honor to the master who sent them is more likely the truth-teller, because he’s not gaining anything personal from it. For instance, Moses gave you the law, and you pat yourselves on the back pretty heartily because you were honored with receiving it. You’re surprised at how much I know, but you’re pretty pleased with yourself for everything you know. But you don’t keep the Law. You have it, but you don’t obey it. So why are you trying to kill me when the Law says, “Do not kill”? What kind of thing is that?
The people are scornful. “You’re demon-possessed. Nobody’s trying to kill you.” They think he’s paranoid. Read back in John 5.18, though, where the people tried to kill him. Jesus wasn’t making this up. (By the way, a story like this is an evidence of authenticity of the text and the historicity of the story. The charge by the people of Jesus being demon-possessed is not likely something the writer would invent.)
Jesus says, “You’re surprised because I know what I do. I also amazed you by doing one miracle. Now, Moses tells you to circumcise your sons, and he tells you to keep the Sabbath day holy. But if it’s a Sabbath when the boy needs to be circumcised, you circumcise him. Well, I healed someone on the Sabbath, so why are you angry with me? You have to be consistent, and stop making superficial judgments.”