Here "sons" stands for those who descended from Heth. See how you translated this in [Genesis 23:3](./03.md). Alternate translation: "the descendants of Heth" (See: [[rc://en/ta/man/translate/translate-names]])
The abstract noun "the hearing" can be stated as "hear" or "listening." Alternate translation: "so that all the sons of Heth could hear him" or "while all the sons of Heth were listening" (See: [[rc://en/ta/man/translate/figs-abstractnouns]])
This tells which sons of Heth were listening. Alternate translation: "all those who had gathered at the gate of his city" (See: [[rc://en/ta/man/translate/figs-distinguish]])