Those struggling to begin a life of prayer often ask how much time they should spend praying. St. Thomas observes that prayer should only last as long as one's devotion. At the heart of his observation is a great concern in Christian prayer. Namely, Christ commanded that we not allow our prayer to become the repetition of empty words, "for your Father knows what you need before you ask him" (Matthew 6:7).
The wisdom of St. Thomas on this point unfolds as we considered what he means by devotion. To be devoted means to be committed to something or someone out of love. It is not really love if we never make someone of whom we are fond a priority of the heart. But whenever we make someone a priority we discover we must understand their concerns and desires, and as we understand these we must win their confidence. They need to know that we really will be responsible with those things which are of concern for them. They need to know that they are really our priority. They permit us to win their confidence in small ways at first, but as we prove ourselves trustworthy, those we love give us greater responsibilities in regard the concerns of their hearts. The more we love, the more devoted we become, and conversely the more devoted we are, the deeper we learn to love until we burn with a true heart to heart friendship.
This in not only true in human relationships - it is true of the Lord himself. He was on fire with love for us before our creation and anxiouly awaited our coming. So that we might learn to trust in his love, He did not force himself on us in his earthly life, but lived mostly in obscurity and poverty, revealing himself and his great love for us only slowly and in small ways until he offered himself for oursakes on the cross. Similarly, he continues to love us in the same way as He knocks on the door of our heart. If He showed us his burning devotion right away, we would not know how to take it, and we might not trust it. So he waits to be invited and is patient in gaining our trust. And he has such great confidence in us, he is never afraid of rejection.
As we see his devotion for us, we discover the desire to be devoted to him grow in our hearts. This is not the fruit of our own spiritual gymnastics. Such a desire is a grace that comes from God alone. Only he can produce this in our hearts. And he gratefully accepts this desire little by little until it grows to full maturity. Just as any desire matures into action, this holy desire expresses itself in fruits of love: mercy to others, longsuffering in the face of great trials, and a deep kind of prayer which becomes a heart to heart with God. In this way, real devotion to the Lord consists a new mutual trust and loving responsibility between God and man. Such devotion characterizes the transformed life pointed to Paul's letter to the Romans. St. John of the Cross describes this life transforming dynamic like a log blazing with fire: it is difficult to see where God ends and the soul begins.
What is the answer to the question about how much time we should spend in prayer? The time we spend reveals the priority of our hearts. If we discover that our priorities are not what they should be, a starting place for prayer is to humbly admit this to the Lord and beg him to show us his loving devotion. Indeed, if in prayer we allow the Lord to reveal his devotion in us, He will become the source of our devotion for Him -- and a holy fire will catch hold of our lives leading us into a fullness of life the Jesus yearns for us to know.