With all due respect, I believe it actually was.And the only one not repeated in the NT
Matt. 12:12
Matt. 24:20 - referring to a time after the LORD's ascension.
Mk.2:12 & 28
Acts 13:14, 27, 42, 44; 15:21, 16:13; 17:2; 18:4
Notice that the Apostles and the gentile congregants were all keeping the Sabbath after the ascension of the LORD.
Also, that at the Church they referred the new converts to go to the synagogue on the Sabbath to hear the Law of Moses read to get a better understanding of what they had just spoken to them.