John Calvin Commentary Numbers 32:1

"Now the children of Reuben and the children of Gad had a very great multitude of cattle: and when they saw the land of Jazer, and the land of Gilead, that, behold, the place was a place for cattle;" — Numbers 32:1 (ASV)

Now the children of Reuben and the children of Gad. In this narrative we see, as if in a mirror, that while each individual is overly attentive to his own private interests, he forgets what is just and right.

Indeed, those who seek their own advantage do not reflect that they are harming others; but it is impossible for them to avoid seeking more than is their due and preferring themselves to others. Thus, they sin against that rule of charity, that we should not seek our own.

The sons of Gad and Reuben, who had a large number of cattle, saw a stretch of rich and fertile land. Self-interest took possession of them, so that it did not occur to them that they were under an obligation to their brothers not to covet for themselves anything special or separate from them.

Nevertheless, there was a specious pretext for this, by which their eyes were blinded: namely, that nothing was taken away from the others, but rather that an addition was made. For in this way, the whole country on the other side of the Jordan continued to be theirs. Besides, they argued, they were spared an inconvenience rather than exposed to a loss, since the progress of their expedition would be less difficult if the group responsible for the cattle stayed there. This would cease to be a burden to the army, which would then be in a better position to advance.

Their association for the war, however, had been established by God and bound them by an unbreakable bond not to desert the rest of the people. It was also a solemn duty (religio) imposed upon them not to alter the boundaries of the inheritance promised by God.

The land of Canaan was assigned to all the descendants of Abraham, in which they were to be contained and to inhabit it as a distinct world. The tribes of Gad and Reuben then transgressed those limits and, at the same time, separated themselves from the body of the Church, as if they desired to be freed from God.

Therefore, we should be all the more on our guard, so that we do not go astray after our own lusts. And when Moses says that they saw, or considered, the land, let us learn to be careful that our eyes, by improper gazes, do not lead us into snares and blind our minds. In this way, our senses can be so deceived by the poisoned sweetness that reason and fairness are completely overthrown.

The Hebrew word,²¹² which we have rendered peculium, means not only cattle and herds but also flocks of sheep. Indeed, almost all the Israelites owned cattle. However, we gather from Moses' words that these two tribes were especially rich in them. Perhaps this was because the district where they lived in Egypt, being better suited for pasture, had encouraged them to apply themselves more earnestly to that way of life, common to all and passed down to them by their ancestors, for it is not probable that they had surpassed the others in this respect during their journey.

²¹² מקנה, mikneh.