On the next day, the multitude that stood on the other side of the sea saw that there was no other boat there, except the one in which his disciples had embarked, and that Jesus hadn't entered with his disciples into the boat, but his disciples had gone away alone.

 Here the argument becomes specifically Jewish in its expression and assumptions and allusions. Jesus had just made a great claim. The true work of God was to believe in him. "Very well," said the Jews, "this is in effect a claim to be the Messiah. Prove it." 