بُلُوغُ الْمَرَامِ
Bulugh al-Maram 255
The Book of Prayer
وَعَنْهُ - رضى الله عنه - { أَنَّ عُمَرَ - رضى الله عنه - مُرَّ بِحَسَّانَ يَنْشُدُ فِي اَلْمَسْجِدِ , فَلَحَظَ إِلَيْهِ , فَقَالَ : "قَدْ كُنْتُ أَنْشُدُ , وَفِيهِ مَنْ هُوَ خَيْرٌ مِنْكَ } . مُتَّفَقٌ عَلَيْهِ . [1]
Narrated [Abu Hurairah (RA)]: Umar came over Hassan while reciting poetry inside the mosque and looked at him sternly, then he (Hassan) said: "I used to recite poetry inside it (the mosque) in the presence of one who is more pious than you [i.e. the Prophet (ﷺ)]". [Agreed upon].
Sunnah.com reference: Book 2, Hadith 127