13 Then answered they and said before the king, That Daniel, which is of the children of the captivity of Judah, regardeth not thee, O king, nor the decree that thou hast signed, but maketh his petition three times a day.
And he prays “constantly” (deeds of virtue or fulfilling the commandments are included as part of prayer) who unites prayer with the deeds required and right deeds with prayer. For the only way we can accept the command to “pray constantly” as referring to a real possibility is by saying that the entire life of the saint taken as a whole is a single great prayer. What is customarily called prayer is, then, a part of this prayer. Now prayer in the ordinary sense ought to be made no less than three times each day. This is evident in the story of Daniel, who prayed three times each day when such great peril had been devised for him.
Verse 13. "Then they answered before the king and said, 'Daniel, who is of the captivity of Judah, has paid no heed to thy law...'" In order to magnify the dishonor involved in this contempt, they speak of the man who showed this contempt for the king's commands as a mere captive.
[AD 253] Origen of Alexandria on Daniel 6:13