Musnad Ahmad 1018:114

'Abd al-Razzaq narrated to us, Dawud ibn Qays al-San'ani informed us, 'Abd Allah ibn Wahb narrated to me, from his father, he said: Fanaj narrated to me, he said: I was working in al-Dinbadh and tending to it, when Ya'la ibn Umayyah arrived as governor over Yemen, and men from the companions of the Prophet, may God bless him and grant him peace, came with him. A man from those who came with him came to me while I was in the crops, diverting water into the crops, and he had walnuts in his sleeve. He sat on a water channel, and he was breaking some of those walnuts and eating them. Then he gestured to Fanaj and said: "O Persian, come here." I drew near to him, and the man said to Fanaj: "Will you guarantee for me that you will plant some of these walnuts by this water?" Fanaj said to him: "What benefit is that to me?" The man said: "I heard the Messenger of God, may God bless him and grant him peace, say with these two ears of mine: 'Whoever plants a tree and patiently perseveres in protecting it and tending to it until it bears fruit, for everything that is consumed from its fruit, he shall have a charity with God.'" Fanaj said to him: "Did you hear this from the Messenger of God, may God bless him and grant him peace?" He said: "Yes." Fanaj said: "Then I guarantee it." He said: "So from it are the walnuts of al-Dinbadh."