When Jesus was led into the wilderness to be tempted and had fasted for forty days and nights, the tempter tempted him to turn stones into bread. The answer Jesus gave was that 'man shall not live by bread alone, but by every word that proceeds from the mouth of God.' It may not be immediately obvious what this reply reveals. But according to the passage being quoted from the Old Testament,
it revealed what was in his heart. This is what the Israelites were told way back then:
"And you shall remember that the LORD your God led you all the way these forty years in the wilderness, to humble you and test you,
to know what was in your heart, whether you would keep His commandments or not. So He humbled you, allowed you to hunger, and fed you with manna which you did not know nor did your fathers know, that He might make you know that man shall not live by bread alone; but man lives by every word that proceeds from the mouth of the LORD."- Deut 8:2-3
Clearly God uses times of hardship to reveal where we put our trust.