Yahya bin Sa'id said: Shu'bah is the most knowledgeable of people about the hadith of Qatadah, what he heard from him and what he did not hear; Hisham is the better memoriser; and Sa'id narrates the most.
Al-Shaykh (al-Bayhaqi) (may Allah have mercy on him) said: Shu'bah, with his superior memory and his knowledge of what he heard from Qatadah and what he did not, Hisham with his superior memory, and Hammam with the soundness of his book and his greater knowledge of what is not part of the hadith, have come together against Ibn Abi Arubah and those who agreed with him in inserting the slave's working into the hadith. In this there is what casts doubt on the istis'a' (making the slave work) being established in this hadith. And what shows that the additional part about the istis'a' in this hadith is from the fatwa of Qatadah is the following.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب العتق / 21378