During the first few decades of the New Testament church, everyone in the church were either Jews or a small number of converts to Judaism. Further, as Jews how did they view the Seventh Day Sabbath? It was unquestionably kept and supported by all sects. Jewish sects had disagreements about various doctrines like the resurrection, see Acts 23:6-8 , but all sects supported the Sabbath. Why? It was the sign signifying who was your God. Were you worshiping the true God of Israel the creator God, or the pagan's sun god. It is the test commandment which they all learned from the first captivity NOT TO BREAK.