Generosity creates wealth that cannot always be counted by the giver.

You rarely see the full effect of what you give. The person you encouraged goes on to do things you never hear about, and encourages others in turn. The accounting is impossible from your side, which is precisely why it should not be attempted.

Give without expecting to observe the result. Most of the good things done for you were done by people who never learned what came of them, and the arrangement seems to work well enough without the receipts.