Abu Hurairah reported the Messenger of Allah ﷺ as saying:

it is better for a man’s belly to be full of pus than to be full of poetry.

Abu ‘Ali said : I have been told that Abu ‘Ubaid said : It means that his heart is full of poetry so much so that it makes him neglectful of the Quran and remembrance of Allah. If the Quran and the knowledge (of religion) are dominant, the belly will not be full of poetry in our opinion. Some eloquent speech is magic. It means that a man expresses his eloquence by praising another man, and he speaks the truth about him so much so that he attracts the hearts to his speech. He then condemns him and speaks the truth about him so much so that he attracts the hearts to another of his speech, as if he spelled the audience by it.

حَدَّثَنَا أَبُو الْوَلِيدِ الطَّيَالِسِيُّ، حَدَّثَنَا شُعْبَةُ، عَنِ الأَعْمَشِ، عَنْ أَبِي صَالِحٍ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ ﷺ
" لأَنْ يَمْتَلِئَ جَوْفُ أَحَدِكُمْ قَيْحًا خَيْرٌ لَهُ مِنْ أَنْ يَمْتَلِئَ شِعْرًا " . قَالَ أَبُو عَلِيٍّ بَلَغَنِي عَنْ أَبِي عُبَيْدٍ أَنَّهُ قَالَ وَجْهُهُ أَنْ يَمْتَلِئَ قَلْبُهُ حَتَّى يَشْغَلَهُ عَنِ الْقُرْآنِ وَذِكْرِ اللَّهِ فَإِذَا كَانَ الْقُرْآنُ وَالْعِلْمُ الْغَالِبُ فَلَيْسَ جَوْفُ هَذَا عِنْدَنَا مُمْتَلِئًا مِنَ الشِّعْرِ وَإِنَّ مِنَ الْبَيَانِ لَسِحْرًا . قَالَ كَأَنَّ الْمَعْنَى أَنْ يَبْلُغَ مِنْ بَيَانِهِ أَنْ يَمْدَحَ الإِنْسَانَ فَيَصْدُقَ فِيهِ حَتَّى يَصْرِفَ الْقُلُوبَ إِلَى قَوْلِهِ ثُمَّ يَذُمَّهُ فَيَصْدُقَ فِيهِ حَتَّى يَصْرِفَ الْقُلُوبَ إِلَى قَوْلِهِ الآخَرِ فَكَأَنَّهُ سَحَرَ السَّامِعِينَ بِذَلِكَ .