4:16-18 Cain cast off all fear of God, and attended no more on God's ordinances. Hypocritical professors, who dissemble and trifle with God, are justly left to themselves to do something grossly scandalous. So they throw off that form of godliness to which they have been a reproach, and of which they deny the power. Cain went out from the presence of the Lord, and we never find that he came into it again, to his comfort. The land Cain dwelt in was called the land of Nod, which means, 'shaking,' or 'trembling,' and so shows the restlessness and uneasiness of his own spirit, or 'the land of a vagabond:' they that depart from God cannot find rest any where else. Those on earth who looked for the heavenly city, chose to dwell in tabernacles or tents; but Cain, as not minding that city, built one on earth. Thus all who are cursed of God seek their settlement and satisfaction here below.
16. presence of the Lord—the appointed place of worship at Eden. Leaving it, he not only severed himself from his relatives but forsook the ordinances of religion, probably casting off all fear of God from his eyes so that the last end of this man is worse than the first (Mt 12:45).
land of Nod—of flight or exile—thought by many to have been Arabia-Petræa—which was cursed to sterility on his account.