No, that is wrong. He knew this payment was a mistake, right? Right. Obviously right. He even did huge actions like starting a new bank account as if he were setting out to intentionally prove and make it undeniable that he knew this payment was a mistake.
The honest thing to do, is to not take the money. You tell the company about the mistake. That is the only honest thing to do.
This is Honesty 101. Did you not have parents? Do you not value honesty as a virtue? Do you know nothing about being a respectable human being? And even if you do not, even if you don't accept any morality nor virtue whatsoever, just from a totally practical self-interested point of view, do you know nothing about what it takes to be successful in a commercial culture such as ours? You don't rip people off! That is a road to ruin and exile.