(Exodus 31:13) commands: "But My Sabbaths shall you keep." The Mekhilta asks what this verse adds to (Exodus 20:10): "You shall not perform any labor." If labor is already prohibited, what does "keeping" the Sabbath add?
The answer parallels the Mekhilta's earlier teaching about (Exodus 23:13). From the explicit prohibition of labor, we know that the thirty-nine categories of forbidden work are prohibited on the Sabbath. But what about shvuth — activities that border on labor without technically qualifying as one of the thirty-nine categories?
"But My Sabbaths shall you keep" introduces the obligation of shvuth. "Keeping" is broader than simply refraining from labor. It encompasses all the precautionary measures, restrictions, and boundary-behaviors that surround and protect the core prohibitions.
The word "Sabbaths" — plural — is also significant. It implies that the obligation of keeping applies to every Sabbath, in every generation, under all circumstances. The plural form extends the obligation across time, ensuring it is understood not as a one-time command but as an ongoing, permanent feature of Jewish life.
This verse became one of the primary Torah-level sources for the entire rabbinic framework of Sabbath restrictions. The thirty-nine labors are derived from "you shall not perform any labor." The additional protective measures are derived from "My Sabbaths shall you keep." Two commands, two layers of Sabbath observance.