en_tn/zep/03/09.md

I will give pure lips to the people

This is another way of saying that God will cause his people to speak what is right. (See: rc://en/ta/man/translate/figs-metonymy)

serve me standing shoulder to shoulder

The people will be united in their desire to serve God, as people are united physically when they stand together with their shoulders touching each other. (See: rc://en/ta/man/translate/figs-idiom)