za.khakh describes being free from impurity, and in one clause making oneself clean.

The predominant use describes persons or heavenly bodies as not meeting a standard of purity: the heavens and stars are said not to do so, while the Nazirites are favorably compared with snow. A separate causative use occurs where the speaker washes and cleanses his hands.

1. Being free from impurity · dominant

   The Qal perfect plural form occurs in clauses about the heavens and stars not meeting the stated standard in Job 15:15 and Job 25:5; the APB renders both clauses with “not clean.” In Lamentations 4:7, the same form describes the Nazirites in a comparison with snow, which the APB renders “purer than snow.”

   Job 15:15Job 25:5Lamentations 4:7
2. Making oneself clean · rare

   In Job 9:30, the first-person Hiphil sequential perfect stands in the conditional clause about washing with snow water and cleansing the speaker's hands with lye. The APB presents the clause as an act of washing and cleansing.

   Job 9:30

In the Anselm Project Bible: The APB presents the Qal clauses as “not clean” in Job 15:15 and Job 25:5 and as “purer than snow” in Lamentations 4:7. In Job 9:30 it renders the surrounding action with “wash myself” and “cleanse my hands”.