Online Source: i-Epistemology.net

And the example of those who spend their wealth seeking means to the approval of Allah and assuring [reward for] themselves is like the garden on high ground which is hit by a downpour. So it yields its fruits in double. And even if it is not hit by a downpour, then a drizzle [is sufficient]. And Allah, of what you do is Seeing (Surah al-Baqarah 2:265)