Immediately after hearing that Jesus expected all of his followers to forgive offenders multiple times every day, this statement was made. It was like," okay? But we are not spiritually able to do this right now", so "show us how to increase our faith". This is a great prayer for any who have been faced with something or someone or some situation that exceeds one's current spiritual state of being. Obedience requires a consistent growing in one's faith. It would be the equivalent of a person who is only able to walk a half a mile, being told by a physician, "you need to run an ultra marathon". The walker would say, "Okay? But show me how to increase my conditioning". Then, over a process of time, as the walker 'obeys' the physician, they will slowly and surely increase their conditioning and be able to run an ultra marathon. Those who are exercise minded automatically understand the concepts that faith can be increased by acts of obedience that are based on scripture. Doing what scripture requires, has the cumulative affect of increasing one's faith, which is the whole range of spiritual experiences.
So… anyone challenged (and who isn't), with something, someone, or some situation that exceeds your current spiritual state of being? Begin by praying the same prayer the earliest followers of Jesus did. Lord, okay? But…"show us how to increase our faith" so we may fully follow follow you, and obey all your commands.