Musnad Ahmad 6:19

'Abd al-Razzaq narrated to us, Isra'il informed us, from Simak, that he heard Musa ibn Talhah narrating from his father, who said: I passed by with the Prophet, may Allah bless him and grant him peace, in the palm groves of Medina. He saw some people at the tops of the palm trees pollinating the trees. He said: "What are these people doing?" They said: They take from the male [pollen] and place it into the female [tree], pollinating it with it. He said: "I do not think that will avail anything." This reached them, so they abandoned it and came down from them. That year, [the trees] did not bear anything. This reached the Prophet, may Allah bless him and grant him peace, and he said: "It was only a thought I had. If it avails anything, then do it, for I am only a human being like you, and a thought may be wrong or right. But whatever I say to you [saying] 'Allah the Almighty said,' I will never lie against Allah the Almighty."