Matthew 9:14

Then the disciples of John approached him, saying, "Why do we and the Pharisees fast often, but your disciples do not fast?"

Matthew 11:2

Now [when] John heard in prison the deeds of Christ, he sent [word] by his disciples

John 3:25

So a dispute occurred on the part of John's disciples with a Jew concerning purification.

John 4:1

Now when Jesus knew that the Pharisees had heard that Jesus was making and baptizing more disciples than John

Proverbs 20:6

Many a person will proclaim his loyalty [for] himself, but a man [who is] trustworthy, who can find?

Matthew 6:16

"Whenever you fast, do not be sullen like the hypocrites, for they make their faces unrecognizable in order that they may be seen fasting by people. Truly I say to you, they have received their reward in full!

Matthew 11:18-19

For John came neither eating nor drinking, and they say, 'He has a demon!'

Mark 2:18-22

And John's disciples and the Pharisees were fasting, and they came and said to him, "{Why} do the disciples of John and the disciples of the Pharisees fast, but your disciples do not fast?"

Luke 5:33-39

And they said to him, "The disciples of John fast often and make prayers--likewise also the [disciples] of the Pharisees--but yours are eating and drinking!"

Luke 18:9-12

And he also told this parable to some who trusted in themselves that they were righteous, and looked down on {everyone else}:

Treasury of Scripture Knowledge

Summary

Then came to him the disciples of John, saying, Why do we and the Pharisees fast oft, but thy disciples fast not?

Bible References

Why

Matthew 6:16
"Whenever you fast, do not be sullen like the hypocrites, for they make their faces unrecognizable in order that they may be seen fasting by people. Truly I say to you, they have received their reward in full!
Matthew 11:18
For John came neither eating nor drinking, and they say, 'He has a demon!'
Proverbs 20:6
Many a person will proclaim his loyalty [for] himself, but a man [who is] trustworthy, who can find?
Mark 2:18
And John's disciples and the Pharisees were fasting, and they came and said to him, "{Why} do the disciples of John and the disciples of the Pharisees fast, but your disciples do not fast?"
Luke 5:33
And they said to him, "The disciples of John fast often and make prayers--likewise also the [disciples] of the Pharisees--but yours are eating and drinking!"
Luke 18:9
And he also told this parable to some who trusted in themselves that they were righteous, and looked down on {everyone else}: