Don't you remember what happened many years ago even as a child? Somebody said a mean word and you still remember it. You'll remember it for all your life. It rankles like a thorn inside of you. I remember I was a poor boy and somebody once said something to me in the schoolyard about my torn stockings. It was over seventy years ago. I didn't forget it. It rankles to this day. Of course, it's silly, but silly or not silly, it was a hurt.
Or when my father couldn't afford to buy me a sled in the wintertime so he made a sled of his own; he took plain boards and made for me a homemade sled. So the boys who could afford a sled used to call it a ‘cheese box’. It was very embarrassing to me. For years and years every winter I hauled out my ‘cheese box’ and there was a barrage of ona’as devarim, of hurtful words. Finally from my bar mitzvah money, I got a dollar and seventy five cents and bought a sled. In those days you could buy a sled for $1.75 – a real sled that came from a factory. I was finally redeemed from that suffering for all those years. To this day I haven't forgotten the cheese box.
And so ona’as devarim can never be retracted. It's a hurt that's forever. And therefore it's lo nitan l’hashivon, you can't pay back a mean word no matter if you repent. He can forgive you, but you can't take it back. It hurts and hurts forever.