Sahih Muslim | Book 30 | Chapter 35

Narrated by Musa b. Talha
Musa b. Talha reported: I and Allah's Messenger (may peace be upon him) happened to pass by people near the date-palm trees. He (the Holy Prophet) said: What are these people doing? They said: They are grafting, i.e. they combine the male with the female

(tree) and thus they yield more fruit. Thereupon Allah's Messenger (may peace be upon him) said: I do not find it to be of any use. The people were informed about it and they abandoned this practice. Allah's Messenger (may peace be upon him) (was later) on informed (that the yield had dwindled), whereupon he said: If there is any use of it, then they should do it, for it was just a personal opinion of mine, and do not go after my personal opinion; but when I say to you anything on behalf of Allah, then do accept it, for I do not attribute lie to Allah, the Exalted and Glorious.

Narrated by Rafi' b. Khadij
Rafi' b. Khadij reported that Allah's Messenger (may peace be upon him) came to Medina and the people had been grafting the trees. He said: What are you doing? They said: We are grafting them, whereupon he said: It may perhaps be good for you if you do not do that, so they abandoned this practice (and the date-palms) began to yield less fruit. They made a mention of it (to the Holy Prophet), whereupon he said: I am a human being, so when I command you about a thing pertaining to religion, do accept it, and when I command you about a thing out of my personal opinion, keep it in mind that I am a human being. 'Ikrima reported that he said something like this.

Narrated by Anas
Anas reported that Allah's Messenger (may peace be upon him) happened to pass by the people who had been busy in grafting the trees. Thereupon he said: If you were not to do it, it might be good for you. (So they abandoned this practice) and there was a decline in the yield. He (the Holy Prophet) happened to pass by them (and said): What has gone wrong with your trees? They said: You said so and so. Thereupon he said: You have better knowledge (of a technical skill) in the affairs of the world.