Daan: donation is that important aspect of the Life of a Human Being which provides him solace even when one gives away his most precious possessions.
Daan is meant to propitiate sins of the yester years. You ask Forgiveness from the Lord for all sins committed knowingly or unknowingly in this or earlier lives.
The virtue of giving away daan lies in the fact that you give away unhesitatingly and without expectation of any return. Giving away daan knowingly and blissfully aware of the so-called watchers never earns you any merit. On other hand you may incur the wrath of God. Such a daan goes waste. Why care for this Life alone when nothing except virtues get carried to next Life.