@Mr.Bultitude
Exodus 34:21 ("on the seventh day you shall rest; in plowing and in harvesting you shall rest") is understood by the Talmud (
Shabbos 70a) as an explicit reference to the prohibition against plowing and harvesting grain on the Sabbath (aside from the general exegetical comparison between the labors involved in building the Tabernacle and the prohibited labors on the Sabbath, which includes plowing and harvesting).