Matthew 17:9-13

9As they were coming down the mountain, Jesus commanded them, “Do not tell anyone about this vision until the Son of Man has been raised from the dead.”

10The disciples asked Him, “Why then do the scribes say that Elijah must come first?”

11Jesus replied, “Elijah does indeed come, and he will restore all things. 12But I tell you that Elijah has already come, and they did not recognize him, but have done to him whatever they wished. In the same way, the Son of Man will suffer at their hands.”

13Then the disciples understood that He was speaking to them about John the Baptist.