Years ago, while studying Scripture, this phrase came to mind:

“The flesh is never satisfied.”

I mentally agreed and went back to studying. A year or two later, as I read Proverbs to my children, this passage caught me by surprise:

Proverbs 15:11 Sheol and Abaddon (Destruction) lie open before YHWH—how much more the hearts of men!

I stopped reading and remarked to them the revelation I got about this concept. A search revealed an even better verse:

Proverbs 27:20 Sheol and Abaddon are never satisfied, nor are the eyes of a person ever satisfied.

…and left it at that. Now prompted to post this, here are a few others confirming this concept:

Proverbs 30
¹⁵The leech has two daughters:
Give and Give.

There are three things that are never satisfied, four that never say, ‘Enough!’:

¹⁶Sheol,
the barren womb,
land never satisfied with water,
and fire that never says, ‘Enough!’

Ecclesiastes 1:8 All things are wearisome, more than one can describe; the eye is not satisfied with seeing, nor the ear content with hearing.

Ecclesiastes 4:8 There is a man all alone, without even a son or brother. And though there is no end to his labor, his eyes are still not content with his wealth: “For whom do I toil and bereave my soul of enjoyment?” This too is futile—a miserable task.

Ecclesiastes 5:10
He who loves money is never satisfied by money, and he who loves wealth is never satisfied by income. This too is futile.

Ezekiel 23 [the whoredom of Oholah (Northern Israel) and Oholibah (Southern Judah)]

The entire Book of Hosea

Ephesians 2:3 All of us also lived among them at one time, fulfilling the cravings of our flesh and indulging its desires and thoughts. Like the rest, we were by nature children of wrath.

Ephesians 4:19 Having lost all sense of shame, they have given themselves over to sensuality for the practice of every kind of impurity, with a craving for more.

1 John 2:16 For all that is in the world—the lust of the flesh, the lust of the eyes, and the pride of life—is not of the Father but of the world.