When the anti-christ Institution called others anti-christ

Rome (Pope Gregory I, A.D.590 TO 604)

"Gregory, bishop by the grace of God to his well-beloved sons, the Roman citizens: It has come to me that certain men of perverse spirit have disseminated among you things depraved and opposed to the holy faith, so that they forbid anything to be done on the day of the Sabbath. What shall I call them except preachers of anti-Christ?" Epistles, b.13:1

But the seventh day is the sabbath of the LORD thy God: in it thou shalt not do any work... Exodus 20:10