Rafi' b. Khadij reported that Allah's Messenger (ﷺ) 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 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.

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ الرُّومِيِّ الْيَمَامِيُّ، وَعَبَّاسُ بْنُ عَبْدِ الْعَظِيمِ الْعَنْبَرِيُّ، وَأَحْمَدُ بْنُ، جَعْفَرٍ الْمَعْقِرِيُّ قَالُوا حَدَّثَنَا النَّضْرُ بْنُ مُحَمَّدٍ، حَدَّثَنَا عِكْرِمَةُ، - وَهُوَ ابْنُ عَمَّارٍ - حَدَّثَنَا أَبُو النَّجَاشِيِّ، حَدَّثَنِي رَافِعُ بْنُ خَدِيجٍ، قَالَ قَدِمَ نَبِيُّ اللَّهِ صلى الله عليه وسلم الْمَدِينَةَ وَهُمْ يَأْبُرُونَ النَّخْلَ يَقُولُونَ يُلَقِّحُونَ النَّخْلَ فَقَالَ ‏"‏ مَا تَصْنَعُونَ ‏"‏ ‏.‏ قَالُوا كُنَّا نَصْنَعُهُ قَالَ ‏"‏ لَعَلَّكُمْ لَوْ لَمْ تَفْعَلُوا كَانَ خَيْرًا ‏"‏ ‏.‏ فَتَرَكُوهُ فَنَفَضَتْ أَوْ فَنَقَصَتْ - قَالَ - فَذَكَرُوا ذَلِكَ لَهُ فَقَالَ ‏"‏ إِنَّمَا أَنَا بَشَرٌ إِذَا أَمَرْتُكُمْ بِشَىْءٍ مِنْ دِينِكُمْ فَخُذُوا بِهِ وَإِذَا أَمَرْتُكُمْ بِشَىْءٍ مِنْ رَأْىٍ فَإِنَّمَا أَنَا بَشَرٌ ‏"‏ ‏.‏ قَالَ عِكْرِمَةُ أَوْ نَحْوَ هَذَا ‏.‏ قَالَ الْمَعْقِرِيُّ فَنَفَضَتْ ‏.‏ وَلَمْ يَشُكَّ ‏.‏