Jesus said that the real barrier to answered prayers is not the size of our faith, but rather the presence of doubt. He pointed out that the disciples' failure to cast out a demon was because of their unbelief, as doubt and unbelief can short-circuit faith, similar to how a thin wire can disrupt electricity.

Faith is so powerful that even faith as small as a mustard seed can move mountains. Therefore, instead of praying for more faith, cry out like the father in Mark 9: 'Lord, I believe; help my unbelief!'

Scripture references: Mark 9:23-25 + Luke 17:5-6