Matthew 17:10
And the disciples asked him: why do the scribes say that first Elijah must come? The disciples' question about Elijah — prompted by Elijah's appearance in the transfiguration — addresses the scribal teaching that Elijah must come first (based on Malachi 4:5) before the messianic age begins. The disciples' question implies: if Elijah must come first and the Messiah has now been revealed, when did Elijah come?