7 “I sought the Lord, and He heard me”. Where heard the Lord? Within. Where gives He? Within. There you pray, there you are heard, there you are blessed. You have prayed, you are heard, you are blessed; and he knows not who stands by you: it is all carried on in secret, as the Lord says in the Gospel, “Enter into your closet, and when you have shut your door, pray to your Father which is in secret; and your Father which sees in secret, shall reward you openly.” When therefore you enter into your chamber, you enter into your heart. Blessed are they who rejoice when they enter into their heart, and find therein nought of evil....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)