To get an understanding of the portion, let’s read Matthew 17:14-21, “And when they were come to the multitude, there came to him a certain man, kneeling down to him, and saying, Lord, have mercy on my son: for he is lunatick, and sore vexed: for ofttimes he falleth into the fire, and oft into the water. And I brought him to thy disciples, and they could not cure him. Then Jesus answered and said, O faithless and perverse generation, how long shall I be with you? how long shall I suffer you? bring him hither to me. And Jesus rebuked the devil; and he departed out of him: and the child was cured from that very hour. Then came the disciples to Jesus apart, and said, Why could not we cast him out? And Jesus said unto them, Because of your unbelief: for verily I say unto you, If ye have faith as a grain of mustard seed, ye shall say unto this mountain, Remove hence to yonder place; and it shall remove; and nothing shall be impossible unto you. Howbeit this kind goeth not out but by prayer and fasting.”

Briefly, here was a man who had a son.  According to Luke 9:38, this was the man’s only son.  He desired mercy from the Lord because he was considered a ‘lunatic’ (one who had seizures, possible epileptic seizures), he was sore vexed (suffered terribly) and falling often into fire or into water.  The Lord determined this young boy suffered from demon possession and drove the demon from him, thus curing him from his many maladies. 

The Lord’s disciples were disappointed and perplexed at their inability to drive the demon from this boy.  The lesson here is one for us all as the Lord explained that to effectively do the Lord’s work, we must be men and women of faith.  What is the faith that should control the believer’s life?  It is a trust in the Lord to do what He determines He will do.  It is trusting Him and His strength, trusting Him and His will, and trusting Him and His timing.  The Lord said they would need faith “as a grain of mustard seed” to be able to do the work of the Lord.

There are two thoughts concerning the meaning of the Lord’s words here.

  • Since the mustard seed was the smallest of seeds known in that area, many see that as saying that even the smallest amount of true faith can produce great works.
  • Although so tiny, the mustard seed would grow to produce the largest of all herbs. Some suppose this means that if you have increasing, expanding, growing faith, you can perform the most difficult tasks successfully. 

There is certainly some credibility to both these encouraging thoughts.  I think we can readily see truthful applications in both of these thoughts, and I thought it would be good for us to consider these things before moving on to your good question. 

You asked why verse 21 is left out of many translations of the Bible.  Actually, this verse is left out in only a few translations.  Most respected and revered versions, such as the KJV, NKJV, NASB, JND, WEB, YLT, and the Amplified Bible all include this verse.  We learn from this that our faithful work for the Lord comes from dependence upon Him and dedication to Him.  Oh, to think what can be accomplished when we put our daily faith in the Lord and depend upon Him to do that which pleases Him and not seek our own desires.  We are taught in 1 Corinthians 7:5 to, “give yourselves to fasting and prayer…”  We read the words of Daniel in Daniel 9:3, “And I set my face unto the Lord God, to seek by prayer and supplications, with fasting, and sackcloth, and ashes.”  Dear reader, much can be accomplished when we pursue the Lord’s guidance, His will, and His power as we seek to serve Him.  (CC)  (702.4)