Genesis 6:5-7

5. And God saw that the wickedness of man was great. Moses prosecutes the subject to which he had just alluded, that God was neither too harsh, nor precipitate in exacting punishment from the wicked men of the world. And he introduces God as speaking after the manner of men, by a figure which ascribes human affections to God; because he could not otherwise express what was very important to be known; namely, that God was not induced hastily, or for a slight cause, to destroy the world. For by the word saw, he indicates long continued patience; as if he would say, that God had not proclaimed his sentence to destroy men, until after having well observed, and long considered, their case, he saw them to be past recovery. Also, what follows has not a little emphasis, that ‘their wickedness was great in the earth.’ He might have pardoned sins of a less aggravated character: if in one part only of the world impiety had reigned, other regions might have remained free from punishment. But now, when iniquity has reached its highest point, and so pervaded the whole earth, that integrity possesses no longer a single corner; it follows, that the time for punishment is more than fully arrived. A prodigious wickedness, then, everywhere reigned, so that the whole earth was covered with it. Whence we perceive that it was not overwhelmed with a deluge of waters till it had first been immersed in the pollution of wickedness.

Every imagination of the thoughts of his heart. Moses has traced the cause of the deluge to external acts of iniquity, he now ascends higher, and declares that men were not only perverse by habit, and by the custom of evil living; but that wickedness was too deeply seated in their hearts, to leave any hope of repentance. He certainly could not have more forcibly asserted that the depravity was such as no moderate remedy might cure. It may indeed happen, that men will sometimes plunge themselves into sin, while yet something of a sound mind will remain; but Moses teaches us, that the mind of those, concerning whom he speaks, was so thoroughly imbued with iniquity, that the whole presented nothing but what was to be condemned. For the language he employs is very emphatical: it seemed enough to have said, that their heart was corrupt: but not content with this word, he expressly asserts, “every imagination of the thoughts of the heart;” and adds the word “only,” as if he would deny that there was a drop of good mixed with it.