looking for a quote from scripture: Because punishment is delayed, people's hearts are hardened.?

It's still close enough for the human mind to recognize it: "Because the sentence of the deed of evil is not executed swiftly; therefore, the heart of the children of men is encouraged to do evil." Ecclesiastes 8:11

per edit: Believe it or not; I only came across this yesterday. Two days ago, I wouldn't have known it, either. :-)

Ecclesiastes 8:11 " Because sentence against an evil work is not executed speedily, therefore the heart of the sons of men is fully set in them to do evil."

Matthew 24:48

But and if that evil servant shall say in his heart, My lord delayeth his coming;

Luke 12:45

But and if that servant say in his heart, My lord delayeth his coming; and shall begin to beat the menservants and maidens, and to eat and drink, and to be drunken;