How was an inheritance divided under the material blessing when there were three sons?
Under the material blessing, the eldest son received a double portion. If there were three sons, the father divided the estate into four parts: the oldest received two parts, and each of the other two sons received one part. This was the firstborn's double inheritance.
Les explains that the material blessing was distinct from the birthright. The birthright did not create enmity between brothers, but the blessing did because it concerned the material side. The material blessing stipulated that the eldest son would get a double portion. So if there were three sons, the father divided the estate into four parts: the oldest got two parts, and the other two each got one part. Les notes that in the context, with two sons, the estate would have been divided into three parts, with the eldest getting two and the other one. Esau was interested in that double portion, which is why he got so upset when he found out Abraham had already given the blessing to Jacob. That meant Jacob would get a double portion of Isaac's wealth, and Jacob was now in the line of the Messiah. Les also reminds us that these people were wealthy, with flocks, herds, servants, and even Abraham had a good collection of gold and silver.