Some people get a change of heart. I hope you find another buyer soon.
It depends on whether or not all the contingencies have been met. Personally, if all the contingencies have been met, I would wait to see if you can find another buyer. And when/if you do find another buyer, you'll be able to tell if this client backing out of the deal has cost you the $14,000 or more.
If you end up selling for $14,000 less (or even less), then you'll have what's commonly called: "damages", and in my mind, be entitled to keep the full amount. If you end up only losing $5,000, you might want to negotiate the $9,000 difference with the former buyer.
Consult with your Realtor, and/or a real estate attorney (if they use those where you are). Good luck.
Why does he want it returned?
Technically, in part, it depends on the reason why the seller is backing out. You're suggesting that the financial contingency has been satisifed. But are there other contingencies that haven't been? If so, then the buyer may be entitled to the return of his earnest money.
Assuming, though, that the buyer has simply gotten cold feet and that you're 100% in the right, you could play tough. Or you could negotiate. Ask your Realtor for advice on that. There's also the question of re-marketing the property and how a protracted battle over the earnest money might affect the timing. Again, your Realtor can advise you on that.
Hope that helps.