The Lord forbid it me - Or, "Yahweh forbid it me." Naboth, as a worshipper of Yahweh, not of Baal, considers it would be wrong for him to comply with the king's request, as contrary to the Law (margin). His was not a mere refusal arising out of a spirit of sturdy independence, or one based upon the sentiment which attaches men to ancestral estates.

And Naboth said to Ahab, the Lord forbid it me that I should give the inheritance of my fathers unto thee. The inheritances of families were not to be alienated to another family, or tribe, nor even to be sold, unless in extreme poverty, and then to return at the year of jubilee, Leviticus 25:23. Now Naboth was a man in good circumstances, and under no necessity of selling his vineyard; and, if he sold it, he might reasonably conclude, it becoming a part of the royal demesnes, would never revert to his family; and therefore, both out of regard to the law of God, and the good of his family, would not part with it at any rate: this shows that he was a conscientious man, and therefore is thought to be one of those that would not bow his knee to Baal, and against whom Ahab had a grudge, and sought an opportunity against him.

Naboth refused to part with the vineyard, because it was the inheritance of his fathers, that is to say, on religious grounds (חלילה כּי מיהוה), because the sale of a paternal inheritance was forbidden in the law (Leviticus 25:23-28; Numbers 36:7.). He was therefore not merely at liberty as a personal right to refuse the king's proposal, but bound by the commandment of God.

And Naboth said to Ahab, The LORD forbid it me, that I should give the inheritance of my fathers unto thee.

21:3 The Lord forbid - For God had expressly, and for divers weighty reasons forbidden the alienation of lands from the tribes and families to which they were allotted. And although these might have been alienated 'till the jubilee, yet he durst not sell it to the king for that time; because he supposed, if once it came into the king's hand, neither he, nor his posterity, could ever recover it; and so he should both offend God, and wrong his posterity.

21:1-4 Naboth, perhaps, had been pleased that he had a vineyard situated so near the palace, but the situation proved fatal to him; many a man's possessions have been his snare, and his neighbourhood to greatness, of bad consequence. Discontent is a sin that is its own punishment, and makes men torment themselves. It is a sin that is its own parent; it arises not from the condition, but from the mind: as we find Paul contented in a prison, so Ahab was discontented in a palace. He had all the delights of Canaan, that pleasant land, at command; the wealth of a kingdom, the pleasures of a court, and the honours and powers of a throne; yet all avails him nothing without Naboth's vineyard. Wrong desires expose men to continual vexations, and those that are disposed to fret, however well off, may always find something or other to fret at.