Matthew 17:19

Then the disciples came to Jesus privately and asked Him, "Why could not we expel the demon?"

When He was alone, the Twelve and the others who were about Him requested Him to explain His figurative language.

After the return of Jesus to the house His disciples asked Him privately, "How is it that we could not expel the spirit?"

Treasury of Scripture Knowledge

Then came the disciples to Jesus apart, and said, Why could not we cast him out?

When He was alone, the Twelve and the others who were about Him requested Him to explain His figurative language.

After the return of Jesus to the house His disciples asked Him privately, "How is it that we could not expel the spirit?"