The Importance of Prayer

Thomas Aquinas prayed five hours a day and walked wherever he went. He could take a jet when he went from Naples to Cologne, but had to walk there. So what was moving him? Was it any sense of reward, merit, being rewarded by the Lord at the end of the day? And this story didn't seem to jibe with that,. We can meet our Lord in prayer, which is, I don't need a reward.