en_tn/gen/49/19.md

Gad ... attack him, but he

Here "Gad" stands for his descendants. Alternate translation: "The descendants of Gad ... attack them, but they" (See: rc://en/ta/man/jit/figs-metonymy)

at their heels

Here "heels" stands for the raiders who are running away from the descendants of Gad. (See: rc://en/ta/man/jit/figs-synecdoche)