I heard the Messenger of Allah ﷺ say: In eloquence there is magic, in knowledge ignorance, in poetry wisdom, and in speech heaviness. Sa'sa'ah ibn Suhan said: The Prophet of Allah ﷺ spoke the truth. His statement "In eloquence there is magic" means: (For example), there is a right due from a man who is more eloquent in reasoning than the man who is demanding his right. He (the defendant) charms the people by his speech and takes away his right. His statement "In knowledge there is ignorance" means: A scholar brings to his knowledge what he does not know, and thus he becomes ignorant of that. His statement "In poetry there is wisdom" means: These are the sermons and examples by which people receive admonition. His statement "In speech there is heaviness" means: That you present your speech and your talk to a man who is not capable of understanding it, and who does not want it.  

سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ إِنَّ مِنَ الْبَيَانِ سِحْرًا وَإِنَّ مِنَ الْعِلْمِ جَهْلاً وَإِنَّ مِنَ الشِّعْرِ حُكْمًا وَإِنَّ مِنَ الْقَوْلِ عِيَالاً فَقَالَ صَعْصَعَةُ بْنُ صُوحَانَ صَدَقَ نَبِيُّ اللَّهِ ﷺ أَمَّا قَوْلُهُ إِنَّ مِنَ الْبَيَانِ سِحْرًا فَالرَّجُلُ يَكُونُ عَلَيْهِ الْحَقُّ وَهُوَ أَلْحَنُ بِالْحُجَجِ مِنْ صَاحِبِ الْحَقِّ فَيَسْحَرُ الْقَوْمَ بِبَيَانِهِ فَيَذْهَبُ بِالْحَقِّ وَأَمَّا قَوْلُهُ إِنَّ مِنَ الْعِلْمِ جَهْلاً فَيَتَكَلَّفُ الْعَالِمُ إِلَى عِلْمِهِ مَا لاَ يَعْلَمُ فَيُجَهِّلُهُ ذَلِكَ وَأَمَّا قَوْلُهُ إِنَّ مِنَ الشِّعْرِ حُكْمًا فَهِيَ هَذِهِ الْمَوَاعِظُ وَالأَمْثَالُ الَّتِي يَتَّعِظُ بِهَا النَّاسُ وَأَمَّا قَوْلُهُ إِنَّ مِنَ الْقَوْلِ عِيَالاً فَعَرْضُكَ كَلاَمَكَ وَحَدِيثَكَ عَلَى مَنْ لَيْسَ مِنْ شَأْنِهِ وَلاَ يُرِيدُهُ