It is narrated from Sayyiduna Ibn Mas'ud (may Allah be pleased with him) that a man was watering his crop when he saw a shading patch (of cloud), from which he heard a voice: Water the land of so-and-so. He followed the voice until he reached the land that had been named. He asked its owner: What do you do with it (that you were given this)? He said: I put back one third (of its produce) into it (the cultivation), I give one third in charity, and I keep one third for my family.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9432