Keeping the Sabbath is an across the board must do for salvation.
Read 1John ch1
.
We must keep the sabbath?
Funny, St Paul went all through the pagan gentile world and spread the Universal Faith and what was the result? A Church that worshipped on the 8th day, not the 7th.
These Gentiles had no clue what the sabbath was or how to keep it. What instructions did St Paul give them in his letters??
Cue the crickets.....................