John 7:15-17 (NIV) - The Jews were amazed and asked, "How did this man get such learning without having studied?" Jesus answered, "My teaching is not my own. It comes from him who sent me. If anyone chooses to do God's will, he will find out whether my teaching comes from God or whether I speak on my own.
The Jews, those in the crowd who followed Him and the rulers and religious leaders who heard Him speak, were amazed at His teaching.
He did not attend the rabbinical schools where scholars spent their days studying the Scriptures (what we know as the Old Testament), yet He spoke with knowledge and authority.
While the religious leaders sat around arguing and debating the meaning of every word of Scripture then imposed myriad commands on the people they were to instruct, Jesus explained with grace and compassion telling them God's truth and allowing them the freedom to believe.
When asked how He, a seemingly lowly, uneducated carpenter's son, knew so much and spoke so authoritatively He replied that His words came from God, the One who sent Him into the world. Jesus taught the true meaning of the Law He had written and given to Moses on that mountain long ago.
He said that anyone who chooses to do God's will knows God's teachings.
Those listening had a choice. They could choose to believe that the words Jesus spoke were from God; and many of them did, then and later.
We who have also chosen to believe know the truth because it is written on our hearts and lived out in our lives with help from His Spirit inside us.