Genesis 8:21

And the Lord smelled a sweet savour
Or a "savour of rest" ^F5; he was delighted and well pleased with his sacrifice, which was offered up in the faith of the sacrifice of Christ; the apostle says, "is for a sweetsmelling savour", ( Ephesians 5:2 ) referring to this passage; that being a satisfaction to the justice of God, an appeasing of his wrath, and a propitiation for the sins of men:

and the Lord said in his heart;
within himself; it was awhile a secret there, but Noah being a prophet, as Aben Ezra observes, he revealed it to him, or "to his heart" ^F6, that is, to the heart of Noah, as some interpret it, he spoke comfortably to him, as follows, when the Jewish writers ^F7 say he stretched out his right hand and swore, agreeably to ( Isaiah 54:9 )

I will not again curse the ground for man's sake,
or drown it for the sin of man, as he had cursed it for the sin of Adam, and which continued till this time; but now was taken off, and it became more fruitful, and very probably by means of the waters which had been so long upon it, and had left a fructifying virtue in it, as the waters of the Nile do in Egypt. Some interpret the phrase, "for man's sake", for the man Christ's sake, for the sake of his sacrifice, of which Noah's was a type, and the sense be, that God would no more curse the earth; for by his sacrifice the curse of the law is removed, with respect to his people; they are redeemed from it, and shall inherit that new earth, of which this earth, renewed after the flood, was a type, in which there will be no more curse, ( Revelation 21:1 ) ( 22:3 ) which sense, though evangelical, cannot be admitted, because of the reason following, unless the first word be rendered "though", as it may:

for the imagination of man's heart [is] evil from his youth;
his nature is depraved, his heart is corrupt, the thoughts of it evil, yea, the imagination of it, and of them, is sinful, and that originally, even from his birth; from the time he is shook out of his mother's womb, as Jarchi interprets the phrase: man is conceived in sin, and shapen in iniquity, and is a transgressor from the womb, and so a child of wrath, and deserving of the curse of the law upon himself, and all that belong to him; and yet this is given as a reason why God will not any more curse the ground for his sake: that which was a reason for destroying the earth, is now one against it, see ( Genesis 6:5 ) which may be reconciled thus, God for this reason destroyed the earth once, for an example, and to display his justice; but such is his clemency and mercy, that he will do it no more to the end of the world; considering that man has brought himself into such a condition, that he cannot but sin, it is natural to him from his birth; his nature is tainted with it, his heart is full of it, and all his thoughts and imaginations are wicked and sinful, from whence continually flow a train of actual sins and transgressions; so that if God was to curse and drown the world as often as man sins, he must be continually doing it; for the words may be rendered, "though the imagination of man's heart is evil" ^F8; yet I will not do it; and so they are expressive of the super abounding grace of God over abounding sin:

neither will I again smite any more everything living, as I have
done;
this hinders not but that there might be, as has been since, partial calamities, or particular judgments on individual persons, towns, and cities, as those of Sodom and Gomorrah, or partial inundations, but not a general deluge, or an universal destruction of the world and creatures in it, at least not by water, as has been, but by fire, as will be; for that the earth will have an end, at least as to its present nature, form, and use, may be concluded from the following words.