Luke 12:21

“So is he who lays up treasure for himself, and is not rich toward God.”

And Jesus then delivered the punch line. That is what happens to those who use their riches for themselves, and are not rich towards God. They end up with nothing but a cold, dark grave, which however splendid men may make it on the outside, is only dark and cold on the inside (see Isaiah 14:10). What a contrast to the one who ascends to enjoy his riches stored up in heaven, because he has come under the Kingly Rule of God and has laid up treasure in Heaven.

Note that the final verdict is not concerning his building up of wealth, it concerns what he does with it once he has built it up. He can lay it up for himself. Or he can be rich towards God (Luke 12:33; Luke 16:9). And he foolishly does the former. (In the light of the previous passage we could say, ‘for every idle penny that a man shall spend he will give account thereof in the Day of Judgment').