For three transgressions of Israel, and for four - In Israel, on whom the divine sentence henceforth rests, the prophet numbers four classes of sins, running into one another, as all sins do, since all grievous sins contain many in one, yet in some degree distinct:
(1) Perversion of justice;
(2) oppression of the poor;
(3) uncleanness;
(4) luxury with idolatry.
They sold the righteous for silver - It is clear from the opposite statement, “that we may buy the poor for silver and the needy for a pair of shoes,” that the prophet is not speaking of judicial iniquity, but of actual buying and selling. The law allowed a Hebrew who was poor to sell himself , and a Hebrew to buy him until the year of release; yet this too with the express reserve, that the purchaser was forbidden to “serve himself with him with the service of a slave, but as a hired servant and a sojourner stroll he be with thee” Leviticus 25:39-40. The thief who could not repay what he stole, was to “be sold for his theft” Exodus 22:2-3. But the law gave no power to sell an insolvent debtor. It grew up in practice. The sons and daughters of the debtor Nehemiah 5:5, or “his wife and children” Matthew 18:25, nay even the sons of a deceased debtor 2 Kings 4:1, were sold. Nehemiah rebuked this sharply. In that case, the hardness was aggravated by the fact that the distress had been fomented by usury. But the aggravation did not constitute the sin. It seems to be this merciless selling by the creditor, with Amos rebukes. The “righteous” is probably one who, without any blame, became insolvent. The “pair of shoes,” that is, sandals, express the trivial price, or the luxury for which he was sold. They had him sold “for the sake of a pair of sandals,” that is, in order to procure them. Trivial in themselves, as being a mere sole, the sandals of the Hebrew women were, at times, costly and beautiful (Song of Solomon 7:1; Ezra 10; Judith 16:9). Such a sale expressed contempt for man, made in the image of God, that he was sold either for some worthless price, or for some needless adornment.