Matthew 9:14

At that time John's disciples came and asked Jesus, "Why do we and the Pharisees fast, but your disciples do not?"

Matthew 11:2

Now John had heard in prison about the Christ's doings, and he sent some of his disciples to inquire:

John 3:25

As the result, a discussion having arisen on the part of John's disciples with a Jew about purification,

John 4:1

Now as soon as the Master was aware that the Pharisees had heard it said, "Jesus is gaining and baptizing more disciples than John"--

Matthew 6:16

"When any of you fast, never assume gloomy looks as the hypocrites do; for they disfigure their faces in order that it may be evident to men that they are fasting. I solemnly tell you that they already have their reward.

Matthew 11:18-19

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

Mark 2:18-22

(Now John's disciples and those of the Pharisees were keeping a fast.)

Luke 5:33-39

Again they said to Him, "John's disciples fast often and pray, as do also those of the pharisees; but yours eat and drink."

Luke 18:9-12

And to some who relied on themselves as being righteous men, and looked down upon all others, He addressed this parable.

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
"When any of you fast, never assume gloomy looks as the hypocrites do; for they disfigure their faces in order that it may be evident to men that they are fasting. I solemnly tell you that they already have their reward.
Matthew 11:18
"For John came neither eating nor drinking, and they say, 'He has a demon.'
Mark 2:18
(Now John's disciples and those of the Pharisees were keeping a fast.)
Luke 5:33
Again they said to Him, "John's disciples fast often and pray, as do also those of the pharisees; but yours eat and drink."
Luke 18:9
And to some who relied on themselves as being righteous men, and looked down upon all others, He addressed this parable.