1 sn The instruction to “open your mouth” is a metonymy of cause; it means “speak up for” (so NIV, TEV, NLT) or in this context “serve as an advocate in judgment” (cf. CEV “you must defend”).
2 sn The instruction compares people who cannot defend themselves in court with those who are physically unable to speak (this is a figure of speech known as hypocatastasis, an implied comparison). The former can physically speak; but because they are the poor, the uneducated, the oppressed, they are unable to conduct a legal defense. They may as well be speechless.
3 tn Or “of all the defenseless.” The noun חֲלוֹף (khalof) means “passing away; vanishing” (properly an infinitive); in this construction “the sons of the passing away” means people who by nature are transitory, people who are dying – mortals. But in this context it would indicate people who are “defenseless” as opposed to those who are healthy and powerful.
