13 “Open me,” he says, “the gates of righteousness”. Behold, we have heard of the gates. What is within? “That I may,” he says, “go into them, and give thanks unto the Lord.” This is the confession of praise full of wonder, “even unto the house of God, in the voice of joy and confession of praise, among such as keep holiday:” this is the everlasting bliss of the righteous, whereby they are blessed who dwell in the Lord's house, praising Him for evermore.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)