It means that if we observe Sunday, we serve Satan instead of God, as the Creator and Giver of Eternal Life, and show our obedience to Satan and not to God!
مرسىىىىىىىىىىىىىىىىىىىىىى ىىىىىىىىىىىىىىىىىىىىىىىىى ىىىىىىىىىىىىىىىىىىىىىىىىى ىىىىىىىىىىىىىىىىىىىىىىىىى ىىى