“Howbeit this kind goeth not out but by prayer and fasting.” Matthew 17:21

Before he made the statement in the main verse, the Bible tells us Jesus had gone up to pray, and when you read the account of Luke, during this period of prayer, he was prepared for his future and his certain destiny.
As he prayed he knew where he ought to be headed- Jerusalem:
“…They were talking with Jesus about his death that would happen in Jerusalem.” Luke 9:31, ERV
He also knew he wasn’t going to Jerusalem to become a physical ruler but to die.
His next location and purpose in that location was made clear to him as he prayed, and read more:
“And it came to pass, that on the next day, when they were come down from the hill, much people met him.” Luke 9:37
He spent a whole day praying and we weren’t told they took anything for food. No time spent praying is a waste; the future might be a mystery to some but not to the man who prays:
“For he that speaketh in an unknown tongue speaketh… unto God… howbeit in the spirit he speaketh mysteries.” 1 Corinthians 14:2

Bible Reading Plan: Job 33, 1 Chronicles 15