When thou tillest the ground. This verse is the exposition of the former; for it expresses more clearly what is meant by being cursed from the earth, namely, that the earth defrauds its cultivators of the fruit of their toil. Should any one object that this punishment had before been alike inflicted on all mortals, in the person of Adam; my answer is, I have no doubt that something of the benediction which had hitherto remained, was now further withdrawn with respect to the murderer, in order that he might privately feel the very earth to be hostile to him. For although, generally, God causes his sun daily to rise upon the good and the evil, (Matthew 5:45,) yet, in the meantime, (as often as he sees good,) he punished the sins, sometimes of a whole nation, and sometimes of certain men, with rain and hail, and clouds, so far, at least, as is useful to give determinate proof of future judgment; and also for the purpose of admonishing the world, by such examples, that nothing can succeed when God is angry with and opposed to them. Moreover in the first murder, God designed to exhibit a singular example of malediction, the memory of which should remain in all ages. A fugitive and a vagabond shalt thou be [1] Another punishment is now also inflicted; namely, that he never could be safe, to whatever place he might come. Moses uses two words, little differing from each other, except that the former is derived from nvnoa, which is to wander, the other from nddnadad, which signifies to flee. The distinction which some make, that nna is he who never has a settled habitations but ndnad, he who knows not which way he ought to turn; as it is defective in proof, is with me of no weight. The genuine sense then of the words is, that wherever Cain might come, he should be unsettled and a fugitive; as robbers are wont to be, who have no quiet and secure resting-place; for the face of every man strikes terror into them; and, on the other hand, they have a horror of solitude. But this seems to some by no means a suitable punishment for a murderer, since it is rather the destined condition of the sons of God; for they, more than all others, feel themselves to be strangers in the world. And Paul complains that both he and his companions are without a certain dwelling-place, (1-Corinthians 4:11 [2] ) To which I answer, that Cain was not only condemned to personal exile, but was also subjected to still more severe punishment; namely, that he should find no region of the earth where he would not be of a restless and fearful mind; for as a good conscience is properly called a brazen walls' so neither a hundred walls, nor as many fortresses, can free the wicked from disquietude. The faithful are strangers upon the earth, yet, nevertheless, they enjoy a tranquil temporary abode. Often, constrained by necessity, they wander from place to place, but wheresoever the tempest bears them, they carry with them a sedate mind; till finally by perpetual change of place, they so run their course, and pass through the world, that they are everywhere sustained by the supporting hand of God. Such security is denied to the wicked, whom all creatures threaten; and should even all creatures favor them, still the mind itself is so turbulent that it does not suffer them to rest. In this manner, Cain, even if he bad not changed his place, could not have shaken off the trepidation which God had fixed in his mind; nor did the fact, that he was the first man who built a city, prevent him from being always restless even in his own nest.

Footnotes

1 - "stenon kai tremon." "Groaning and trembling." -- Sept

2 - "Instabiles esse conqueritur."

A fugitive and a vagabond shalt thou be - Thou shalt be expelled from the presence of God, and from thy family connections, and shalt have no fixed secure residence in any place. The Septuagint render this στενων και τρεμων εση, thou shalt be groaning and trembling upon the earth - the horror of thy crime shall ever haunt thee, and thou shalt never have any well-grounded hope that God will remit the punishment thou deservest. No state out of endless perdition can be considered more awful than this.

When thou tillest the ground, it shall not henceforth yield unto thee her strength; a (l) fugitive and a vagabond shalt thou be in the earth.
(l) You will never have rest for your heart will be in continual fear and worry.

When thou tillest the ground,.... Which was the business he was brought up in and followed, Genesis 4:2.
it shall not henceforth yield unto thee her strength; the earth had been cursed for Adam's sin, and was not so fruitful as in its original state; and now it was cursed again for Cain's sin; not the whole earth, but that part which belonged to Cain, and was cultivated by him; and so it must be supposed to be cursed, not only in the spot where he had been settled, but in every other place where he should come and occupy, and which through this additional curse became so barren that it did not yield such good fruits, and such an increase of it as before; it lost its native and vital juice, by which seed cast into it became not so fruitful, and did not increase; but instead of this, though much pains were taken to manure it, and much was sown, yet it brought forth little, at least but little to Cain, whatever it did to others; and therefore it is said, "shall not yield unto thee"; it would not turn much to his account, or yield much profit and increase to him, or bring forth much fruit; see Job 31:38.
a fugitive and a vagabond shalt thou be in the earth; being obliged to quit his former habitation, and remove to a place at some distance from the house of his father Adam, which was near the garden of Eden, as Aben Ezra observes; and to wander about from place to place, having no quiet settlement in anyone place: the Septuagint render it "groaning and trembling"; the guilt of his sin lay heavy on his conscience, and filled him with such horror and terror that he was continually sighing and groaning, and was seized with such a tremor that he shook in all his limbs; so the Arabic writers (t) say, that he was trembling and quivering, and had a shaking in his head all the days of his life; and Aben Ezra observes, that there are some that say that the first of these words signifies to moan and lament; but it may be, it was not so much his sin, at least the evil of it, that he lamented, as the mischief that came by it, or the calamities and misfortunes it brought upon him.
(t) Patricides, apud Hottinger. Smegma Oriental. l. 1. c. 8. p. 223.

a fugitive--condemned to perpetual exile; a degraded outcast; the miserable victim of an accusing conscience.