Fourth Century
Canon 29, of the Council of Laodicea (a.d. 364), shows that the ecclesiastical system was laboring to put an end to Sabbath keeping:
"Christians shall not Judaize and be idle on Saturday [the Sabbath], but shall work on that day; but the Lord's day [as they called Sunday] they shall especially honor, and, as being Christians, shall, if possible, do no work on that day. If, however, they be found Judaizing, they shall be shut out from Christ."—Hefele, "History of the Councils of the Church," Vol. II, book 6, sec. 93, canon 29.
Fifth Century
Sozomen's Ecclesiastical History shows Rome evidently leading in the effort to abolish any recognition whatever of the Sabbath:
"The people of Constantinople, and of several other cities, assemble together on the Sabbath, as well as on the next day; which custom is never observed at Rome, or at Alexandria."—Book 7, chap. 19.
Seventh Century
There were true Sabbath keepers in Rome itself, teaching the truth of God among the people, and bringing upon themselves the denunciation of Pope Gregory the Great, who wrote "to his most beloved sons the Roman citizens:"
"It has come to my ears that certain men of perverse spirit have sown among you some things that are wrong and opposed to the holy faith, so as to forbid any work being done on the Sabbath day. What else can I call these but preachers of Antichrist?"—"History of the Councils" (Labbe and Cossart), Vol. V, col. 1511; see also "Nicene and Post-Nicene Fathers," Vol. XIII, book 13, epistle 1.