Sahih Muslim | Book 30 | Hadith Number 5831

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.