Urwah (may Allah have mercy on him) said: When Allah, the Mighty and Majestic, granted the Messenger of Allah (peace and blessings be upon him) the conquest of Khaybar, and he (peace and blessings be upon him) killed those of them whom he killed, Zaynab bint al-Harith, the Jewess, who was the daughter of Marhab's brother, sent a roasted sheep as a gift and put poison in it, and she put more poison in the shoulder and the foreleg when she was told that these were the parts of the sheep most beloved to the Messenger of Allah (peace and blessings be upon him). When the Messenger of Allah (peace and blessings be upon him) entered, and with him (peace and blessings be upon him) was Sayyiduna Bishr bin al-Bara' bin Ma'rur (may Allah be pleased with him), a man of Banu Salamah, she presented it to the Messenger of Allah (peace and blessings be upon him). He (peace and blessings be upon him) took the shoulder and the foreleg and bit off from it, and Bishr (may Allah be pleased with him) took another bone and bit from it. When the Messenger of Allah (peace and blessings be upon him) swallowed the morsel in his mouth, Bishr (may Allah be pleased with him) also swallowed what was in his mouth. Then the Messenger of Allah (peace and blessings be upon him) said: "Hold back your hands, for the shoulder of the sheep is telling me that it has been poisoned." Bishr bin al-Bara' (may Allah be pleased with him) said: By the One who honoured you, I sensed that in the morsel that I ate, and nothing prevented me from spitting it out except that I disliked spoiling your food. Then when you (peace and blessings be upon him) swallowed what was in your mouth, I did not hold myself back from you, and I hoped that what I had swallowed might not have poison in it. Bishr (may Allah be pleased with him) did not rise from his place until his colour became like a taylasan (shawl), and his pain kept afflicting him continuously, until he could not turn over by himself unless (others) turned him. And the Messenger of Allah (peace and blessings be upon him) lived three years after that, until the illness in which he (peace and blessings be upon him) passed away came upon him.
Hadith Referenceالمعجم الكبير للطبراني / باب الباء / 1193