What does Genesis 43:9 mean?

Judah and his brothers are pushing Jacob to make a tough decision. One option is to risk losing his beloved youngest son Benjamin by sending him to Egypt with his brothers, as required by the Egyptian ruler who sells the grain (Genesis 42:3–6). The other is to allow the family to starve to death in the continuing famine (Genesis 43:1–2), including the "little ones" (Genesis 43:8).

Now Judah promises to take personal responsibility for Benjamin's safety. More than that, he offers himself as a pledge of safety. This language indicates a serious commitment; this is not a casual promise. Judah is literally offering his own life in exchange for Benjamin if he fails to bring the boy back to Jacob alive and well. It's unclear what the exact consequence would be, but he would accept the blame "forever."

Reuben had made a similar offer to Jacob earlier, suggesting that Jacob could kill his own two sons if he failed to return Benjamin (Genesis 42:37). Jacob rejected that, preferring to abandon Simeon (Genesis 42:19–20, 24) to keep Benjamin safe. He will reluctantly and fearfully accept this suggestion from Judah (Genesis 43:11–14).