Or HaChaim on Deuteronomy 33:20/אור החיים על דברים ל״ג:כ׳

1 מרחיב גד, "the One who enlarges Gad." G'd had enlarged Gad's properties as we know from Numbers 32,1 where the Torah tells us that the tribe possessed large numbers of cattle and sheep. The reason they had so much cattle is also mentioned in Numbers 31,53 that the soldiers each plundered as much as they could. Seeing that the men of Gad were renowned as fighting men they garnered more for themselves than the other tribes. Moses' simile "like a lion who is at rest after he has brought the torn off limbs of his prey," accurately reflects what happened.