(Al-Baqara) 2 : 265
وَمَثَلُ الَّذِينَ يُنْفِقُونَ أَمْوَالَهُمُ ابْتِغَاءَ مَرْضَاتِ اللَّهِ وَتَثْبِيتًا مِنْ أَنْفُسِهِمْ كَمَثَلِ جَنَّةٍ بِرَبْوَةٍ أَصَابَهَا وَابِلٌ فَآتَتْ أُكُلَهَا ضِعْفَيْنِ فَإِنْ لَمْ يُصِبْهَا وَابِلٌ فَطَلٌّ ۗ وَاللَّهُ بِمَا تَعْمَلُونَ بَصِيرٌ
The similitude of those who are spending their wealth seeking Lord Allah’s satisfaction and with confidence by their souls is just like a garden on a hilltop affected with heavy rain, then it provides its crops in double, then even if not affected by heavy rain, a drizzling is enough; Allah is observing whatever you are doing.
See explanation 2: 62 and 7: 205-206.