Chief priests and captains - See the notes at Matthew 26:14. See the account of the bargain which Judas made with them explained in the Matthew 26:14-16 notes, and Mark 14:10-11 notes.
Absence of the multitude - The multitude, “the people,” were then favorable to Jesus. He had preached in the temple, and many of them believed that he was the Messiah. It was a hazardous thing, therefore, to take him by force, and in their presence, as they might rise and rescue him. Hence, they sought to take him when “he” was away from the multitude; and as Judas knew of a place where he could be found “alone,” they were glad of the opportunity of so easily securing him.