Purity in the camp. Infectious people to be segregated. A test for women suspected of infidelity.
I imagine the test is one of those cultural relative issues. Seems primitive to us but probably a lot gentler than treatment of women in the rest of the ancient world.
Meta message: God judges, husband’s don’t own wives like chattels. Jealousy must be proven.
But gee whiz… No remedy for male cheating?