Jesus knew that John's authority came from heaven. He asked the question so the Jewish leaders would have to tell what they thought to all who were listening. AT: "Do you think John's authority to baptize people came from heaven or from men?" or "Do you think God told John to baptize people, or did people tell him to do it?"
"from God." Jewish people avoided referring to God by his name "Yahweh." Often they used the word "heaven" to refer to him. (See: [[rc://en/ta/man/translate/figs-metonymy]])