Bible Study - Matthew 17:19-21

Matthew 17:19–21 KJV 1900

19 Then came the disciples to Jesus apart, and said, Why could not we cast him out? 20 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. 21 Howbeit this kind goeth not out but by prayer and fasting.

Abstract

This study of Matthew 17:14-21 (KJV) encourages believers to overcome shortcomings in their faith by understanding the necessity of seeking, trusting, and acting upon their belief in Christ. When the disciples struggled to cast out a demon, Jesus highlighted their lack of faith and instructed them on the power of unwavering trust in God. By asking about faith (Matthew 17:19), believers acknowledge their spiritual deficiencies. Through assurance of faith (Matthew 17:20), they learn that even faith as small as a mustard seed can produce mighty works. Finally, activating faith (Matthew 17:21) through prayer and fasting deepens reliance on God’s power. Cross-references such as James 1:5-6, Hebrews 11:6, and Philippians 4:13 reinforce that overcoming faith’s shortcomings requires seeking divine wisdom, believing God’s promises, and putting faith into action.

Introduction

Every believer experiences moments of weakness and doubt, struggling to fully grasp the depth of faith that Christ calls us to have. Even the disciples—who walked with Jesus, witnessed His miracles, and heard His teachings firsthand—encountered situations where their faith was insufficient. In Matthew 17:14-21, they faced an instance where their inability to cast out a demon led them to question why they had failed. This passage serves as a crucial lesson in recognizing and overcoming the shortcomings in our faith.

Faith is not merely intellectual agreement but a dynamic trust in God’s power and promises. When the disciples failed to heal the afflicted boy, Jesus pointed out their lack of faith, demonstrating that even those closest to Him had room for growth. The reality of weak or wavering faith should not lead to despair but to a deeper pursuit of Christ, for He is the one who strengthens and perfects our belief. Matthew 17:20 reminds us that faith, even as small as a mustard seed, can move mountains, teaching us that it is not the size of our faith but the object of our faith—Jesus—that truly matters.

As we examine how to overcome shortcomings in our faith, we will explore three key aspects: asking about faith (Matthew 17:19), assurance of faith (Matthew 17:20), and activating faith (Matthew 17:21). By addressing our doubts, embracing Christ’s promises, and applying spiritual disciplines, we can cultivate a faith that moves mountains and stands firm in the face of adversity.

I. Ask About Faith (Matthew 17:19)

The disciples’ failure to cast out the demon led them to ask Jesus, “Why could not we cast him out?” (Matthew 17:19, KJV). This question reveals an essential truth: acknowledging our shortcomings is the first step toward spiritual growth. Asking about faith demonstrates humility, a willingness to learn, and a desire for greater spiritual power. Proverbs 2:3-6 encourages us to cry out for wisdom and understanding, showing that seeking divine guidance is necessary for overcoming faith deficiencies.

Faith is not static; it must be nurtured through persistent inquiry and reflection on God’s Word. The disciples recognized that something was lacking in their spiritual authority, and instead of ignoring the issue, they sought an answer from Jesus. Likewise, believers must be willing to confront their struggles in faith, bringing their questions before the Lord in prayer. James 1:5-6 instructs us to ask God for wisdom in faith, assuring us that He gives generously to those who seek Him.

Furthermore, questioning one’s faith is not a sign of weakness but an invitation to greater understanding. Many biblical figures, from Abraham (Genesis 15:2-6) to Thomas (John 20:27-29), sought reassurance in their faith journeys. Jesus’ response to the disciples shows that He welcomes such inquiries, using them as opportunities to teach and strengthen their belief. By asking about faith, believers position themselves to receive divine revelation and power.

Synopsis of "Ask About Faith" (Matthew 17:19)

Asking about faith is an act of humility and dependence on God. The disciples’ question in Matthew 17:19 illustrates the importance of seeking divine guidance when faith appears insufficient. God honors sincere inquiries by revealing greater spiritual truths (Jeremiah 33:3) and leading believers into a deeper understanding of His will (Psalm 25:4-5).

Five Truths About "Ask About Faith"

Faith must be examined.

2 Corinthians 13:5 “5 Examine yourselves, whether ye be in the faith; prove your own selves. Know ye not your own selves, how that Jesus Christ is in you, except ye be reprobates?”

Seeking wisdom strengthens faith.  

James 1:5–6 “5 If any of you lack wisdom, let him ask of God, that giveth to all men liberally, and upbraideth not; and it shall be given him. 6 But let him ask in faith, nothing wavering. For he that wavereth is like a wave of the sea driven with the wind and tossed.”

God welcomes our questions.

Jeremiah 33:3 “3 Call unto me, and I will answer thee, and shew thee great and mighty things, which thou knowest not.”

Humility leads to greater understanding.  

Proverbs 2:3–6 “3 Yea, if thou criest after knowledge, And liftest up thy voice for understanding; 4 If thou seekest her as silver, And searchest for her as for hid treasures; 5 Then shalt thou understand the fear of the Lord, And find the knowledge of God. 6 For the Lord giveth wisdom: Out of his mouth cometh knowledge and understanding.”

Faith grows through divine revelation 

Romans 10:17 “17 So then faith cometh by hearing, and hearing by the word of God.”

II. Assurance of Faith (Matthew 17:20)

Jesus responded to the disciples’ inquiry by pointing to the power of unwavering faith: “If ye have faith as a grain of mustard seed… nothing shall be impossible unto you” (Matthew 17:20, KJV). Assurance of faith is confidence in God’s power, knowing that He will fulfill His promises. Hebrews 11:6 reminds us that “without faith it is impossible to please him,” emphasizing that true faith requires full trust in God’s ability to work beyond human limitations.

The mustard seed, though small, represents faith that is alive and growing. Just as a seed, when planted, develops into a strong tree, faith must be nurtured through prayer, study, and obedience. Philippians 4:13 reinforces this assurance, affirming that through Christ, we can accomplish all things.

Believers must reject doubt and embrace the certainty of God’s promises. Faith is not based on emotions but on God’s unchanging Word (Isaiah 40:8). Those who stand firm in their faith, even amid trials, will experience the supernatural work of God (Mark 9:23).

Synopsis of "Assurance of Faith" (Matthew 17:20)

Assurance of faith is rooted in trust in God’s power. Jesus assures us that even small faith yields great results when placed in Him (Matthew 17:20). By standing on God’s promises (Hebrews 11:6), believers can overcome doubt and experience spiritual breakthroughs.

Five Truths About "Assurance of Faith"

Faith in God makes all things possible.

Mark 9:23 “23 Jesus said unto him, If thou canst believe, all things are possible to him that believeth.”

Faith grows like a seed.

Matthew 13:31–32 “31 Another parable put he forth unto them, saying, The kingdom of heaven is like to a grain of mustard seed, which a man took, and sowed in his field: 32 Which indeed is the least of all seeds: but when it is grown, it is the greatest among herbs, and becometh a tree, so that the birds of the air come and lodge in the branches thereof.”

Doubt hinders faith.  

James 1:6–8 “6 But let him ask in faith, nothing wavering. For he that wavereth is like a wave of the sea driven with the wind and tossed. 7 For let not that man think that he shall receive any thing of the Lord. 8 A double minded man is unstable in all his ways.”

God rewards faith.  

Hebrews 11:6 “6 But without faith it is impossible to please him: for he that cometh to God must believe that he is, and that he is a rewarder of them that diligently seek him.”

Faith overcomes obstacles 

1 John 5:4 “4 For whatsoever is born of God overcometh the world: and this is the victory that overcometh the world, even our faith.”

III. Activate Faith (Matthew 17:21)

Faith must be exercised through action. Jesus emphasized that certain spiritual victories require prayer and fasting (Matthew 17:21). Faith grows stronger when believers engage in spiritual disciplines that deepen reliance on God (Acts 13:2-3).

Prayer connects us to God’s power, while fasting disciplines the flesh. When combined, these practices increase spiritual sensitivity and authority. Jesus Himself modeled this (Luke 4:1-2), demonstrating that faith becomes active when believers seek God wholeheartedly.

Living faith requires bold steps. James 2:17 teaches that faith without works is dead. As believers activate faith through prayer, obedience, and perseverance, they experience the fullness of God’s power at work.

Synopsis of "Activate Faith" (Matthew 17:21)

Faith must be exercised through prayer and fasting (Matthew 17:21). Spiritual growth requires commitment, and those who actively seek God will experience divine breakthroughs (James 2:17).

Five Truths About "Activate Faith"

Prayer strengthens faith.

Mark 11:24 “24 Therefore I say unto you, What things soever ye desire, when ye pray, believe that ye receive them, and ye shall have them.”

Fasting deepens spiritual authority.

Acts 13:2–3 “2 As they ministered to the Lord, and fasted, the Holy Ghost said, Separate me Barnabas and Saul for the work whereunto I have called them. 3 And when they had fasted and prayed, and laid their hands on them, they sent them away.”

Faith requires action 

James 2:17 “17 Even so faith, if it hath not works, is dead, being alone.”

Spiritual battles need spiritual weapons

Ephesians 6:10–18 “10 Finally, my brethren, be strong in the Lord, and in the power of his might. 11 Put on the whole armour of God, that ye may be able to stand against the wiles of the devil. 12 For we wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places. 13 Wherefore take unto you the whole armour of God, that ye may be able to withstand in the evil day, and having done all, to stand. 14 Stand therefore, having your loins girt about with truth, and having on the breastplate of righteousness; 15 And your feet shod with the preparation of the gospel of peace; 16 Above all, taking the shield of faith, wherewith ye shall be able to quench all the fiery darts of the wicked. 17 And take the helmet of salvation, and the sword of the Spirit, which is the word of God: 18 Praying always with all prayer and supplication in the Spirit, and watching thereunto with all perseverance and…”

God adds to those who seek Him.

Matthew 6:33 “33 But seek ye first the kingdom of God, and his righteousness; and all these things shall be added unto you.”