I and Messenger of Allah ﷺ 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 Messenger of Allah ﷺ said: I do not find it to be of any use. The people were informed about it and they abandoned this practice. Messenger of Allah ﷺ (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.  

مَرَرْتُ مَعَ رَسُولِ اللَّهِ ﷺ بِقَوْمٍ عَلَى رُءُوسِ النَّخْلِ فَقَالَ مَا يَصْنَعُ هَؤُلاَءِ فَقَالُوا يُلَقِّحُونَهُ يَجْعَلُونَ الذَّكَرَ فِي الأُنْثَى فَيَلْقَحُ فَقَالَ رَسُولُ اللَّهِ ﷺ مَا أَظُنُّ يُغْنِي ذَلِكَ شَيْئًا قَالَ فَأُخْبِرُوا بِذَلِكَ فَتَرَكُوهُ فَأُخْبِرَ رَسُولُ اللَّهِ ﷺ بِذَلِكَ فَقَالَ إِنْ كَانَ يَنْفَعُهُمْ ذَلِكَ فَلْيَصْنَعُوهُ فَإِنِّي إِنَّمَا ظَنَنْتُ ظَنًّا فَلاَ تُؤَاخِذُونِي بِالظَّنِّ وَلَكِنْ إِذَا حَدَّثْتُكُمْ عَنِ اللَّهِ شَيْئًا فَخُذُوا بِهِ فَإِنِّي لَنْ أَكْذِبَ عَلَى اللَّهِ ﷻ  

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.  

قَدِمَ نَبِيُّ اللَّهِ ﷺ 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  

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.  

أَنَّ النَّبِيَّ ﷺ مَرَّ بِقَوْمٍ يُلَقِّحُونَ فَقَالَ لَوْ لَمْ تَفْعَلُوا لَصَلُحَ قَالَ فَخَرَجَ شِيصًا فَمَرَّ بِهِمْ فَقَالَ مَا لِنَخْلِكُمْ قَالُوا قُلْتَ كَذَا وَكَذَا قَالَ أَنْتُمْ أَعْلَمُ بِأَمْرِ دُنْيَاكُمْ