Luther on Jacob was a plain man (Genesis 25:27).

[GHansen]

Now let us also look at the second part of the antithesis: “While Jacob was a man תָּם, dwelling in tents.” All have translated תָּם with “simple,” “foolish,” although the Hebrew text does not have this meaning. For תָּם does not denote one who is simple in mind and intellect, that is, without ingenuity and industry. No, it denotes one who is simple, upright, blameless, and sincere in regard to his will. The same word occurs in Ps. 119:1: “Blessed are the blameless.” For, as is evident later on when he buys the birthright from his brother, Jacob is not dull. Lyra [medieval commentator] even explains it in this manner: “Without a trace of deceit, not simple on account of a lack of industry.” Esau was not such a man; but in regard to his will he was far more unstable and cunning, because he married heathen wives and mingled with the Canaanites. Hunters are not blameless, but they often adapt their pursuits to the difference in the times, the situations, and the persons. Jacob, however, is simple and steadfast, is not influenced by persons and is not changed by events. Nevertheless, he is not foolish. This is a fine comparison.

In the second place, Jacob is not a man of the fields. He has no political and carnal pursuits—although affairs of state can be administered in a godly and proper manner—but he dwelt exclusively in tents; that is, he remained at home with his father and mother, and served them. Lyra tells what the Jews thought about the tents. I am in complete accord with what he has to say, because it is taken from the fathers. They say that tents not only for the households but also for the churches are meant. Thus one speaks of the tent of Moses and means a sacred tent. We call them churches and schools. But at that time there was no difference between the sacred tents and those occupied by households. Abraham had in his tent a house of God and a church, just as today any godly and pious head of a household instructs his children and domestics in godliness. Therefore such a house is actually a school and church, and the head of the household is a bishop and priest in his house. Thus the tents in which Jacob dwelt were sacred, and there he sought first the kingdom of God (Matt. 6:33). Esau, on the other hand, sought the kingdom of the world. Therefore he lost both, namely, the worldly and the spiritual kingdom, because it is a general and perpetual rule that for those who seek first the kingdom of God the other things are added. On the other hand, to those who want to get their own advantages and their daily bread before being concerned about the kingdom of God the opposite will happen; they will lose the kingdom of God together with the physical kingdom.

Luther, M. (1999). Luther’s works, vol. 4: Lectures on Genesis: Chapters 21-25. (J. J. Pelikan, H. C. Oswald, & H. T. Lehmann, Eds.) (Vol. 4, pp. 383–384). Saint Louis: Concordia Publishing House.