The Prophet ﷺ said, "For one of your bellies to be filled with pus that festers within him is better for him than to be filled with poetry."Hajjaj said, "I heard Yunus bin Jubayr."
حدثنا محمد بن جعفر حدثنا شعبة وحجاج حدثني شعبة عن قتادة عن يونس بن جبير عن محمد بن سعد
عن النبي ﷺ قال لأن يمتلئ جوف أحدكم قيحا يريه خير له من أن يمتلئ شعرا قال حجاج سمعت يونس بن جبير
Its isnad is sahih. Muslim related it in 2:199 from Muhammad bin Muthanna and Muhammad bin Bashshar, from Muhammad bin Jafar. Tirmidhi and Ibn Majah also related it, as noted in Dhakhair 5/208.Yureehi, from al-wary, with a fatha on the waw and a saakin ra, meaning the disease. Jawhari said, "The pus consumed his insides, yareehi, wariyan, meaning it ate at him," or it is from the lung (riah), and its root is also from al-wary. So the meaning of yureehi is that it strikes his lung.As for the statement at the end of the hadith, "Hajjaj said, I heard Yunus bin Jubayr," this does not mean that Hajjaj heard directly from Yunus, but rather that Qatada explicitly stated that he heard it from Yunus, within the isnad that Hajjaj related.