Daraqutni

Sayyiduna Ibn Umar (may Allah be pleased with them both) narrates: The Noble Prophet (peace and blessings be upon him) had a Muslim killed in retaliation for a treaty-bound (dhimmi) person. He said: "I am the most entitled to fulfill the protection I have granted." This narration has only been transmitted as musnad by Ibrahim bin Abi Yahya, who is abandoned in hadith; the correct version is that this narration is transmitted as mursal from Ibn Bilmani, who is weak. Such a narration cannot be used as proof, even if he has transmitted it as a connected narration, let alone when he has transmitted it as mursal. And Allah knows best.