If you ever make a promise to do something unreasonable in the case of something extremely unlikely and it actually happens, it is a test of morals.
For example, if you promise to give someone the winnings of a lottery ticket and you actually win, you most certainly would not have won if you didn't promise it.
What you now have isn't a fortune, but essentially a karma time bomb. Fulfill your end of the bargain or find out why you should have.