(31:13) "but My Sabbaths shall you keep": What is the intent of this? From (Ibid. 20:10) "You shall not perform any labor," I would know only of labor per se. Whence would I derive (the same for) shvuth ("resting," things bordering upon labor)? It is, therefore, written "but My Sabbaths shall you keep," to include shvuth.
What Does Keeping the Sabbath Add
Mekhilta Tractate Shabbata 1:2