Mark 9:28

When He had gone indoors, His disciples began asking Him privately, “Why were we unable to drive it out?”

Mark 7:17

When Jesus had left the crowd and gone into the house, His disciples asked Him about the parable.

Matthew 13:10

Then the disciples came to Him and asked, “Why do You speak to the crowds in parables?”

Matthew 13:36

Then He left the crowds and went into the house. And His disciples came to Him saying, “Explain [clearly] to us the parable of the weeds in the field.”

Matthew 15:15

Peter asked Him, “Explain this parable [about what defiles a person] to us.”

Matthew 17:19-20

Then the disciples came to Jesus privately and asked, “Why could we not drive it out?”

Mark 4:10

As soon as He was alone, those who were around Him, together with the twelve [disciples], began asking Him about [the interpretation of] the parables.

Mark 4:34

and He did not say anything to them without [using] a parable; He did, however, explain everything privately to His own disciples.

Treasury of Scripture Knowledge

Summary

And when he was come into the house, his disciples asked him privately, Why could not we cast him out?

Bible References

Asked

Mark 4:10
As soon as He was alone, those who were around Him, together with the twelve [disciples], began asking Him about [the interpretation of] the parables.
Matthew 13:10
Then the disciples came to Him and asked, “Why do You speak to the crowds in parables?”
Matthew 15:15
Peter asked Him, “Explain this parable [about what defiles a person] to us.”

Why

Matthew 17:19
Then the disciples came to Jesus privately and asked, “Why could we not drive it out?”

General references

2 Kings 20:10
Hezekiah answered, “It is easy for the shadow to go forward ten steps; no, but let the shadow turn backward ten steps.”
Matthew 17:19
Then the disciples came to Jesus privately and asked, “Why could we not drive it out?”
Mark 10:10
In the house the disciples began questioning Him again about this.