Bitter Water
Bitter water shows up in two distinct settings — the wilderness spring at Marah and the priestly ordeal in Numbers 5. The two scenes share the language of bitterness but use it for opposite purposes: at Marah the bitterness is the problem and a tree is cast in to remove it; in the ordeal the bitterness is the testing instrument itself, drunk by a woman under suspicion of adultery.
The Bitter Waters at Marah
After three days in the wilderness of Shur with no water, Israel reaches a spring whose water cannot be drunk. The naming is from the taste: "And when they came to Marah, they could not drink of the waters of Marah, for they were bitter: therefore it was named Marah" (Ex 15:23). The people complain against Moses (Ex 15:24), and the answer comes through a tree: "And he cried to Yahweh; And [the Speech of] Yahweh showed him a tree, and he cast it into the waters, and the waters were made sweet. There he made for them a statute and an ordinance, and there he proved them" (Ex 15:25). Bitterness becomes the occasion for an ordinance and a test of trust; the tree-in-the-water is the sign that the bitter is not what Yahweh is leaving them with.
The Water of Bitterness in the Sotah Ordeal
The priestly ordeal of jealousy uses bitter water in the opposite direction: it is the means of testing, not the thing being remedied. The priest sets the suspected wife before Yahweh, loosens her hair, and places the meal-offering of jealousy in her hands, "and the priest will have in his hand the water of bitterness that causes the curse" (Nu 5:18). The oath is double-edged. The priest says to the woman, "If no man has plowed you, and if you have not gone aside to uncleanness, being under your husband, [then] be innocent from this water of bitterness that causes the curse" (Nu 5:19), but if she has been defiled, then "Yahweh will make you a curse and an oath among your people, when [the Speech of] Yahweh makes your thigh to fall away, and your body to swell; and this water that causes the curse will go into your insides, and make your body to swell, and your thigh to fall away" (Nu 5:21-22). The woman's response is "Amen, Amen" (Nu 5:22).
The bitterness is then made literal in the procedure. The curses are written in a book and blotted into the water: "And the priest will write these curses in a book, and he will blot them out into the water of bitterness: and he will make the woman drink the water of bitterness that causes the curse; and the water that causes the curse will enter into her [and become] bitter" (Nu 5:23-24). The meal-offering is waved, a handful burned, and "afterward will make the woman drink the water" (Nu 5:25-26). The ordeal closes with the conditional outcome: "if she is defiled, and has committed a trespass against her husband, that the water that causes the curse will enter into her [and become] bitter, and her body will swell, and her thigh will fall away: and the woman will be a curse among her people" (Nu 5:27).
The two passages mirror each other. At Marah, bitter water threatens the people and Yahweh sweetens it; in the priestly ordeal, water made bitter by the inscribed curse becomes either harmless or destructive depending on the woman's truthfulness. In one scene the bitterness is removed; in the other it is the instrument that discriminates innocence from guilt.