Sunan Abi Dawud, Hadith 4503

Qatadah transmitted the tradition mentioned above through a chain of narrators like that of Shu'bah. This version adds: Then al-Hasan forgot this tradition, and he used to say: A free man is not to be killed for a slave.

حَدَّثَنَا الْحَسَنُ بْنُ عَلِيٍّ، حَدَّثَنَا سَعِيدُ بْنُ عَامِرٍ، عَنِ ابْنِ أَبِي عَرُوبَةَ، عَنْ قَتَادَةَ، بِإِسْنَادِ شُعْبَةَ مِثْلَهُ زَادَ ثُمَّ إِنَّ الْحَسَنَ نَسِيَ هَذَا الْحَدِيثَ فَكَانَ يَقُولُ ‏ "‏ لاَ يُقْتَلُ حُرٌّ بِعَبْدٍ ‏" ‏ ‏.‏

sunnah.com

also referenced under: Hadith 4517 (DarusSalam)

It was narrated from Hisham, from Qatadah, from Al-Hasan, who said: "A free man should not be subjected to retaliation in return for a slave."

حَدَّثَنَا مُسْلِمُ بْنُ إِبْرَاهِيمَ، حَدَّثَنَا هِشَامٌ، عَنْ قَتَادَةَ، عَنِ الْحَسَنِ، قَالَ لاَ يُقَادُ الْحُرُّ بِالْعَبْدِ ‏.‏

sunnah.com

also referenced under: Hadith 4518 (DarusSalam)