(Exodus, Ibid. 10) "And the seventh day is Sabbath to the L–rd your G–d. You shall not perform any labor." What is the intent of this? (Exodus 31:15) "Everyone who does labor on the seventh day, die, he shall die" tells us of the punishment. Whence do we derive the exhortation? From "And the seventh day … you shall not perform any labor." This tells me only of the punishment and the exhortation for the labor of the day. Whence do I derive (the same for) the labor of the night? From (Ibid. 14) "those who desecrate it (subsuming both day and night), die, he shall die." This tells me only of punishment (for labor at night). We have not yet heard the exhortation. It is, therefore, written "And the seventh day is Sabbath to the L–rd your G–d. Let "Sabbath" not be mentioned (i.e., "seventh day" is sufficient). It is mentioned to include the night in the exhortation.