Majma al-Zawaid — Hadith 10146

Urwah narrates: On the occasion of the Battle of the Confederates, the Prophet (peace and blessings be upon him) had his wives enter one of the tall buildings (fortresses) of Madinah. Sayyiduna Hassan bin Thabit (may Allah be pleased with him) was a faint-hearted man, so the Prophet (peace and blessings be upon him) placed him with the women as well, and he shut the door. A Jew came and sat at the door of that building. Sayyidah Safiyyah bint Abd al-Muttalib (may Allah be pleased with her) said: "O Hassan! Go down to this lout and kill him." He said: "I am not capable of killing this lout." So Sayyidah Safiyyah (may Allah be pleased with her) wrapped a cloak around herself, took a fihr (a stone for grinding medicine), went down to him and cut off his head.
Al-Tabarani recorded it, and its narrators up to Urwah are the narrators of the Sahih; however,
this narration is "mursal" (lacking the Companion in its chain).