Jesus came to the feast in secret, and the Judeans were trying to find Jesus. Eventually, at night, the Jesus taught at the temple, and the Judeans had a question on how Jesus knew so much without studying (at least in their knowledge). As suggested in Jesus's later comments, the peeps likely asked the question because they wanted to disprove Jesus's authority.
To answer the question, Jesus states that his teaching comes from the Father (7:16). Even though Jesus and Father are the same God (same character), they have distinctness as seen when the Father sends Jesus and provides doctrine. But because Jesus and God are the same God (have the same character), Jesus's will is the same as the will of the Father.
In fact, Jesus talks about how to do His will, knowledge of the doctrine (teaching) from God is important -- whether it is from Father or Son (7:17). Additionally, Jesus talks about how the one who " seeks the One who sent Him is true" and does not have unrighteousness (7:18). Jesus meant that when we focus on the Father, we aren't in a state of having unrighteousness (and the contrapositive is true, too).
Finally, Jesus addressed the heart of the Judeans. He knew that the attitude was accusatory, so he talked about how the Judeans failed to keep all of the Law of Moses. He even asked why they want to kill Jesus, too (7:19).