Imam al-Shafi'i (may Allah have mercy on him) said: "This is also narrated from Sayyiduna Umar and Sayyiduna Ali (may Allah be pleased with them both)."
Al-Shaykh (may Allah have mercy on him) said: "Abdullah bin Ahmad bin Hanbal (may Allah have mercy on him) narrated it in Kitab al-'Ilal from Abu al-Rabi' al-Zahrani, from Hushaym, from Sa'id bin Abi Arubah, from Matar, from al-Hasan, from al-Ahnaf bin Qays, from Sayyiduna Umar and Sayyiduna Ali (may Allah be pleased with them both), concerning a free man who kills a slave; they both said: 'His price (is to be paid), however much it may be.'"
And this chain is sahih (authentic).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / Q15956
Amr bin Shu'ayb narrated from his father, from his grandfather, that Sayyiduna Umar (may Allah be pleased with him) said: If a free man kills a slave, then what is due for him is his price.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 15956
Sa'id bin al-Musayyib (may Allah have mercy on him) narrated from Sayyiduna Umar (may Allah be pleased with him), concerning a slave who is killed, that his price is due in return for him.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 15957
Al-Hasan (may Allah have mercy on him) and Sa'id bin al-Musayyib (may Allah have mercy on him) said, concerning a slave who is killed by mistake, that what is due for him is his price.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 15958
This same narration is reported from Abd al-Karim, from Ali and Abdullah (may Allah be pleased with them both) and Shurayh (may Allah have mercy on him), that his price is to be paid, even if it exceeds the blood money of a free man.
There is irsal (a break in the chain) between him and Abd al-Karim.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 15959
Sayyiduna Anas bin Malik (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "That I sit with a people remembering Allah from Fajr until sunrise is dearer to me than everything upon which the sun rises; and that I sit with a people remembering Allah from after Asr until sunset is dearer to me than freeing eight slaves from the descendants of Isma'il whose blood money is twelve thousand."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 15960