Matthew 9:14

Then John's disciples came to him and said, why do the Pharisees, as well as we, observe so many fasts, and your disciples keep none?

Matthew 11:2

in the mean time John having heard in his confinement of the actions of Christ, he sent two of his disciples to ask him,

John 3:25

Now there happen'd to be a dispute about baptism between a Jews, and some of John's disciples:

John 4:1

Jesus therefore knowing the Pharisees had heard that he made more disciples, and baptized more than John,

Matthew 6:16

When ye fast, don't put on a dismal air, as the hypocrites do, who look dejected, that men may take notice of their fasting: I assure you, they have their reward.

Matthew 11:18-19

so John came with fasting and abstinence, and they say, he is mad.

Mark 2:18-22

It was customary for the Pharisees, and the disciples of John, to fast; they came therefore and ask'd him, why do John's disciples, and the Pharisees fast so frequently, and not your disciples?

Luke 5:33-39

and likewise those of the Pharisees, are frequently fasting and praying, while yours are employed in eating and drinking?

Luke 18:9-12

Then he propos'd this parable, concerning those who had a great opinion of their own justice, and look'd with contempt upon others.

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 ye fast, don't put on a dismal air, as the hypocrites do, who look dejected, that men may take notice of their fasting: I assure you, they have their reward.
Matthew 11:18
so John came with fasting and abstinence, and they say, he is mad.
Mark 2:18
It was customary for the Pharisees, and the disciples of John, to fast; they came therefore and ask'd him, why do John's disciples, and the Pharisees fast so frequently, and not your disciples?
Luke 5:33
and likewise those of the Pharisees, are frequently fasting and praying, while yours are employed in eating and drinking?
Luke 18:9
Then he propos'd this parable, concerning those who had a great opinion of their own justice, and look'd with contempt upon others.