Contradiction with Mark 2:27
While Exodus 31:12 emphasizes the sacredness of the Sabbath as a covenant, Mark 2:27 suggests that the Sabbath was made for man's benefit, potentially downplaying its obligatory nature.
Mark 2:27: And he said unto them, The sabbath was made for man, and not man for the sabbath:
Contradiction with Romans 14:5
This verse implies that observing a specific day, like the Sabbath, is a personal conviction, which could contradict the strict commandment seen in Exodus 31:12.
Romans 14:5: One man esteemeth one day above another: another esteemeth every day [alike]. Let every man be fully persuaded in his own mind. [fully persuaded: or, fully assured]