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.