Al-Nawawi reported: Al-Shafi’i, may Allah have mercy on him, said, “If a prophetic narration is authenticated and it contradicts my opinion, act according to the narration and abandon my opinion.”
Source: al-Majmū’ Sharḥ al-Muhadhab 1/104
عن النووي عَنْ الشَّافِعِيِّ قَالَ رَحِمَهُ اللَّهُ إذَا صَحَّ الْحَدِيثُ خِلَافَ قَوْلِي فَاعْمَلُوا بِالْحَدِيثِ وَاتْرُكُوا قَوْلِي
1/104 المجموع شرح المهذب