Thomas Aquinas

And he said to them: go you also into my vineyard. Because God rewards according to justice. 1 Samuel 26:23: God will reward according to justice. With these he did not agree upon a denarius. Why with the first, and not with these? The reason is, according as it refers to the age of the world: because Adam was going to sin, he could therefore be excused if he had not known his remuneration; but he knew, because he had tasted. Likewise, he who has better senses, truth is more clearly known to him. …

Commentary on Matthew ↗