Continued commentaryThe mark of the beast is the opposite of this--the observance of the first day of the week. This mark distinguishes those who acknowledge the supremacy of the papal authority from those who acknowledge the authority of God. {8T 117.4}
(In comment on Revelation 14:J9-12): John was called to behold a people distinct from those who worship the beast or his image by keeping the first day of the week. The observance of this day is the mark of the beast.--TM 133 (1898)