The Mekhilta continues its detailed mapping of the Egyptian punishments at the Red Sea, this time connecting the drowning to the specific suffering of slave labor.
The Egyptians had "embittered their lives with hard toil, with mortar" (Exodus 1:14). The Israelite slaves were forced to make bricks from mortar — a thick, clay-like slime that they mixed with their hands and feet, day after grueling day. Mortar was the material of their oppression, the substance of their misery.
God's response transformed the waters of the Red Sea into the same substance. "You, likewise, made the water like slime for them, and they sank in it." The sea did not simply drown the Egyptians with clean, flowing water. It became thick and viscous — like the very mortar the slaves had been forced to mix. The Egyptian soldiers found themselves trapped in the same sticky, suffocating medium they had imposed upon Israel.
The proof texts are vivid. "They were mired in the Red Sea" (Exodus 15:4) — the word "mired" specifically connotes being stuck in slime, not simply submerged in water. The same word appears in (Psalms 69:3): "I am sunk in the slime of the depths," and in the story of the prophet Jeremiah, who was thrown into a cistern where "Jeremiah sank in the slime" (Jeremiah 38:6).
The Mekhilta's point is unmistakable. The Egyptian soldiers did not experience an ordinary drowning. They experienced the exact sensation they had inflicted: sinking into thick, choking slime, the mortar of their own cruelty turned against them.