How can man pray continually, as the body becomes ill through constant prayer? What limit ought there be to prayer? And suppose I am talking with someone, how can I fulfill the command?
The standing up of a man in his prayer [once] is not said to be prayer, but he must do so continually. Whether you are eating, or drinking, or even traveling on the road, or if you are doing some piece of work, you shall not let prayer be remote from your heart.
No measure has been laid down to prayer; because He said, ‘Pray at all times, and continually.’ He did not lay down any measure to prayer. For if you only really pray when you stands up in prayer, then you do not pray with the heart but with the mouth only.
Now concerning this, the Apostle spoke, in all your prayers, and in all your supplications, pray at all times in the spirit; and when it would be inappropriate for you to pray, because you are speaking with another man, then pray through supplication.