It seems as if the Torah in this week’s parshah, Ki Sisa, was concerned that the fourth of the Aseres Hadibros, which speaks of shemiras Shabbos, might not be properly understood. Because smack in the middle of “Operation Mishkan,” — encompassing the previous two parshiyos and the next two parshiyos — the narrative stops abruptly with a firm warning that seems to be a sudden change of topic.