Musnad Ahmad 343:2

'Abd al-Razzaq narrated to us, Dawud ibn Qays al-San'ani informed us, he said: 'Abd Allah ibn Wahb narrated to me, from his father, he said: Fanj 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 approached 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 began breaking those walnuts and eating them. Then he gestured to Fanj and said: "O Persian, come here." He said: I drew near to him, and the man said to Fanj: "Will you guarantee for me the planting of these walnuts by this water?" Fanj said to him: "What benefit is there for me in that?" 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 is patient in preserving it and tending to it until it bears fruit, for him in everything that is taken from its fruit is a charity with God, the Almighty and Majestic.'" Fanj said to him: "Did you hear this from the Messenger of God, may God bless him and grant him peace?" He said: "Yes." Fanj said: "Then I guarantee it." He said: So from it are the walnuts of al-Dinbadh.