Cleanness of teeth - Scarcity of bread, as immediately explained. Ye shall have no trouble in cleaning your teeth, for ye shall have nothing to eat.
Yet have ye not returned unto me, saith the Lord - This reprehension is repeated live times in this chapter; and in it are strongly implied God's longsuffering, his various modes of fatherly chastisement, the ingratitude of the people, and their obstinate wickedness. The famine mentioned here is supposed to be that which is spoken of 2 Kings 8:1; but it is most likely to have been that mentioned by Joel, chaps. 1 and 2.
And I, I too have given you - Such had been their gifts to God, worthless, because destitute of that which alone God requires of His creatures, a loving, simple, single-hearted, loyal obedience. So then God had but one gift which He could bestow, one only out of the rich storehouse of His mercies, since all besides were abused - chastisement. Yet this too is a great gift of God, a pledge of His love, who willed not that they should perish; an earnest of greater favors, had they used it. It is a great gift of God, that He should care for us, so as to chasten us. The chastisements too were no ordinary chastisements, but those which God forewarned in the law, that He would send, and, if they repented, He would, amid the chastisements, forgive. This famine God had sent everywhere, “in all their cities,” and “in all their places,” great and small. Israel thought that its calves, that is, nature, gave them these things. “She did not know,” God saith, “that I gave her corn and wine and oil;” but said, “These are my rewards that my lovers have given me” Hosea 2:8, Hosea 2:12. In the powers and operations of “nature,” they forgat the God and Author of nature. It was then the direct corrective of this delusion, that God withheld those powers and functions of nature. So might israel learn, if it would, the vanity of its worship, from its fruitlessness. Some such great famines in the time of Elijah and Elisha 2 Kings 8:1-6 Scripture records; but it relates them, only when God visibly interposed to bring, or to remove, or to mitigate them. Amos here speaks of other famines, which God sent, as He foretold in the law, but which produced no genuine fruits of repentance.
And ye returned not unto Me - He says not, that they “returned not at all,” but that they “returned not wholly, quite back to God”. Nay the emphatic saying, “ye did not return quite to Me,” so as to reach Me, implies that they did, after a fashion, return. Israel‘s worship was a half, halting 1 Kings 18:21, worship. But a half-worship is no worship; a half-repentance is no repentance; repentance for one sin or one set of sins is no repentance, unless the soul repent of all which it can recall wherein it displeased its God. God does not half-forgive; so neither must man half-repent. Yet of its one fundamental sin, the worship of nature for God, Israel would not repent. And so, whatever they did was not that entire repentance, upon which God, in the law, had promised forgiveness; repentance which stopped short of nothing but God.