مُسْنَدُ أَحْمَدَ
Musnad Ahmad 1507
Musnad Abu Ishaq Sa'd bin Abi Waqqas
It was narrated from "Umar bin Sa"d bin Malik, from Sa"d (رضي الله عنه), that The Messenger of Allah (ﷺ) said: “If the belly of one of you were to be filled with pus that corrodes it, that would be better than filling (his mind) with poetry."
Musnad Ahmad 1507Sahih Hadith; its isnad is Hasan, see the previous report]