Should I expect a reward when doing a good deed? Like I pick up a wallet containing a big amount of money. Shoud I expect a reward from the owner when returning it to him.
No, I don't think you can expect it. But you can take it if it is offered. We can reasonably expect what we are owed. In this case, you literally aren't owed anything because you didn't do all that much. We can't be owed what we don't earn. (Even if the the owner of the wallet exclaims, "Oh, boy, I owe you. Gee, thanks!" and scampers off without giving you a dime.) In your example, I assume that you find the wallet on the street. Or in the seat of a taxi cab. Or anyplace. We just stumble on them. Even returning them often isn't difficult. So no, doing these minor good deeds is simply part of being a decent person. But this doesn't mean you can't graciously accept a reward if it is offered. And I think it is nice to offer, to celebrate the decency of that wallet-bearing stranger. And by the way, if you set out to a good deed on the understanding that you will be rewarded if you succeed (as in, help me find my cat and I'll give you ten bucks), then you rightly have a claim on the reward.