Abu Rafi' (may Allah have mercy on him) said: Abu Lu'lu'ah was the slave of Sayyiduna al-Mughirah bin Shu'bah (may Allah be pleased with him). Then he narrated the whole story and said that he made a double-edged dagger and poisoned it. He said: Sayyiduna Umar (may Allah be pleased with him) said the takbir; Sayyiduna Umar (may Allah be pleased with him) used to speak a little after the iqamah and then say the takbir. He (may Allah be pleased with him) said: "Straighten your rows." And he (the killer) was standing right there in the row. When he (may Allah be pleased with him) said the takbir for the Fajr prayer, he attacked him and wounded his shoulder and his side, and Sayyiduna Umar (may Allah be pleased with him) fell. He wounded 13 (thirteen) more people, of whom 6 (six) died. Sayyiduna Umar (may Allah be pleased with him) was lifted up and carried away. Then he narrated the long hadith. He said: Then Sayyiduna Umar (may Allah be pleased with him) asked for something to drink in order to see the depth of his wound. Nabidh was brought, and it came out of his wound; it could not be known whether it was nabidh or his blood. Then he asked for milk and drank it, and it too flowed out of his wound. The people said: "O Commander of the Believers! Do not worry, nothing will happen." He (may Allah be pleased with him) said: "If there is any harm in being killed, then I have been killed."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 16015