This kind of demon does not go out except by prayer and FASTING

[tonychanyt]

Fasting and prayer were sometimes paired in the OT. BSB, Psalm 35:

13 Yet when they were ill, I put on sackcloth; I humbled myself with fasting, but my prayers returned unanswered.

Daniel 9:

3 Then I turned my face to the Lord God, seeking him by prayer and pleas for mercy with fasting and sackcloth and ashes.

There was no guarantee that fasting and prayer would always change an outcome. David committed adultery and murder in 2 Samuel 12:

15 Then Nathan went to his house.
And the Lord afflicted the child that Uriah’s wife bore to David, and he became sick. 16 David therefore sought God on behalf of the child. And David fasted and went in and lay all night on the ground.

In the end, the child still died.

In the Gospels, the disciples could not cast out a demon in a boy. They brought him to Jesus, and Jesus cast it out. Jesus explained their failure in (ESV) Mark 9:

28 After Jesus had gone into the house, His disciples asked Him privately, “Why couldn’t we drive it out?”
29 Jesus answered, “This kind cannot come out, except by prayer d.”

d BYZ and TR prayer and fasting

Some manuscripts had an additional word "fasting".

A parallel account in Matthew 17:

21 “But this kind [of demon] does not go out except by prayer and fasting.”

Pulpit Commentary:

This verse is omitted in many good manuscripts.

Another parallel account in Luke 9:

42 Even while the boy was coming, the demon threw him to the ground in a convulsion. But Jesus rebuked the impure spirit, healed the boy and gave him back to his father. 43 And they were all amazed at the greatness of God.

Luke did not record the explanation of the prayer or fasting.

Later in Acts 13:

2 While they were worshiping the Lord and fasting, the Holy Spirit said, “Set apart for me Barnabas and Saul for the work to which I have called them.” 3 So after they had fasted and prayed, they placed their hands on them and sent them off.

It is not just prayer but prayer and fasting to humble ourselves before an important decision. Fasting served to intensify prayer, Acts 14:

23 Paul and Barnabas appointed elders for them in each church and, with prayer and fasting, committed them to the Lord, in whom they had put their trust.

In both cases, the disciples fasted before making the crucial appointments that had long-reaching consequences. Fasting solemnizes the souls to listen to God.

Prayer and fasting help you focus on God more singularly and intensely. They can also improve your hearing from God. However, they do not guarantee that your prayer will come true.