[DouglasKC]

It seems to have been the custom not to keep the sabbath in the 2nd Century, since by that time the majority of Christians were no longer Jews. The destruction of the Temple and the exclusion of Christians from the synagogues left Christians on their own. There is the implication here that Christians were the only ones at fault.

Possibly, but the biggest reason seems to have been anti-semitism on the part of the early church. The letter from Constatine certainly shows the attitude of hatred that many of that time felt toward the Jews.

[sola gracia]

There are no commands to keep the Sabbath in the New Testament.

[RobbyS]

Antisemitism is not an apt term, unless you look at the ongoing cultural war between Greeks and Jews that go back to the Maccabees and realize that the Greeks especially were glad to have access to Jewish monotheism without Jewish particularism. The Jews displayed great hostility against the Christians from the beginning, even if we minimize the charges made in the New Testament. The end of Temple Worship was also an end to any common worship. Hebrews is the Christian reaction to that event; the Jewish reaction is to move elements of temple worship to the synagogue.