Why does Matthew 17:21 exist only as a footnote in the King James Bible and not as a verse?
Matthew 17:21 is the last sentence in Jesus’ answer to one of His disciple’s question. Jesus had given His disciples power to cast out demons, but they could not cast out the demon causing a man to be a lunatic. Jesus casts out the demon and then explains why they could not. There is an interesting lesson for us. Jesus had no problem casting out the demon. He had given His disciples power to cast out demons (Matt. 10:5-8), but they could not do what Jesus did. Why? Some will say they lacked faith but Jesus explains that even with faith they did not have the power of Jesus for instantaneous exorcism. They had to pray.
And when they came to the multitude, a man came up to Him, falling on his knees before Him, and saying, “Lord, have mercy on my son, for he is a lunatic, and is very ill; for he often falls into the fire, and often into the water. And I brought him to Your disciples, and they could not cure him.” And Jesus answered and said, “O unbelieving and perverted generation, how long shall I be with you? How long shall I put up with you? Bring him here to Me.” And Jesus rebuked him, and the demon came out of him, and the boy was cured at once. Then the disciples came to Jesus privately and said, “Why could we not cast it out?” And He said to them, “Because of the littleness of your faith; for truly I say to you, if you have faith as a mustard seed, you shall say to this mountain, ‘Move from here to there,’ and it shall move; and nothing shall be impossible to you. “But this kind does not go out except by prayer and fasting.” (NASB) Matt. 17:14-21
Jesus’ statement, “But this kind does not go out except by prayer and fasting” is Matthew 17:21.
The passage is not in several Bibles. Here are some of them: New Century Version (NCV), New International Version (NIV), Contemporary English Version (CEV), and the New Living Translation (NLT). The verse is not included in the newer Bibles because the older and better manuscripts of Matthew do not include it. The translators of the older Bibles were not as careful in the manuscripts they used. Apparently in the process of copying the manuscripts, someone at a much later date copied the verse from the Gospel of Mark and added it to the Matthew account. Here is the Mark account.
And He said to them, “This kind cannot come out by anything but prayer.” (NASB) Mark 9:29
The only difference is that “fasting” is left out.
But this does not change the actual events or words that were spoken. In fact, we should always study all of the gospels – Matthew, Mark, Luke and John – to see what happened during each event in Jesus’ life. When He preached or when He healed someone, each gospel writer may added his own unique account because he heard something different, or the Holy Spirit wanted to emphasize something new. Together the gospels give us a complete picture of what happened in Jesus’ life. So the account in Matthew should be compared to the one in Mark. When we do this, we should include Mark 9:29 because it happened. For some reason, the Holy Spirit did not have it recorded in the gospel of Matthew.