John Calvin on James 1:8

8 A double-minded man, or, a man of a double mind. This sentence may be read by itself, as he speaks generally of hypocrites. It seems, however, to me to be rather the conclusion of the preceding doctrine; and thus there is an implied contrast between the simplicity or liberality of God, mentioned before, and the double-mindedness of man; for as God gives to us with a stretched out hand, so it behooves us in our turn to open the bosom of our heart. He then says that the unbelieving, who have tortuous recesses, are unstable; because they are never firm or fixed, but at one time they swell with the confidence of the flesh, at another they sink into the depth of despair. “The double-minded,” or the man with two souls, δίψυχος, means here no doubt the man who hesitates between faith and unbelief, because faith is the subject of the passage. When again used, in James 4:8, it means a hesitation between God and the world.

James 1:9-11

9 Let the brother of low degree rejoice in that he is exalted:

9 Porro glorietur frater humilis in sublimate sua;

10 But the rich, in that he is made low: because as the flower of the grass he shall pass away.

10 Dives autem in humilitate sua, quia tanquam flos herbae prateteribit.

11 For the sun is no sooner risen with a burning heat, but it withereth the grass, and the flower thereof falleth, and the grace of the fashion of it perisheth: so also shall the rich man fade away in his ways.

11 Nam sol exortus est cum aestu, et exarescit herba, et flos ejus cecidit, et decor aspectus ejus periit; sic et dives in suis viis (vel, copiis) marcescet.