Re: The devil has no hold on a righteous man.
Here's another one:
Mat 18:20 For where two or three are gathered in my name, there am I in the midst of them."
Sounds to me more as a prescription for enhancing the effectiveness of prayer rather than a commandment, nevertheless...
Than again, there are numerous examples of good Christians living and worshiping alone. An example that comes to mind is Saint Anthony, who is also famous for his Temptations in the desert, which I found relevant to my experience.
I too feel that God, in his perfection, would probably prefer a heart-based voluntary service and affection to that done by the scripture but insencire. I think this was one of the most important messages of Jesus:
Rom 7:6 But now we are delivered from the law, that being dead wherein we were held; that we should serve in newness of spirit, and not [in] the oldness of the letter.
In fact, this seems to be also confirmed by the prophecy of the OT about the Messianic age when God would inscribe the Law in man's heart. (don't remember the exact sripture)
Then again, there is, I am somewhat sadened to report, comandmends to 'fear' God, perhaps open for interpretation:
i.e. Serve the Lord with fear, and rejoice before him.