Sayyidah Safiyyah bint Abd al-Muttalib (may Allah be pleased with her) narrates: When the Prophet (peace and blessings be upon him) went out to the Trench (Khandaq), he placed the women in a tall fortified building called "Fari'", and appointed Sayyiduna Hassan bin Thabit (may Allah be pleased with him) with them. Sayyiduna Hassan (may Allah be pleased with him) kept watching the Prophet (peace and blessings be upon him): when the Prophet (peace and blessings be upon him) advanced towards the polytheists, he too would move forward inside the fortress, and when he fell back, he too would move back. Sayyidah Safiyyah (may Allah be pleased with her) says: Some people from the Jews came, and one of them climbed up towards the fortress until he reached us. I said to Hassan: "Get up, go to him and kill him." He said: "I cannot do this; if I were capable of anything, I would have gone with the Messenger of Allah." So Sayyidah Safiyyah (may Allah be pleased with her) struck the head of that (Jew) and cut it off. When she had cut it off, Sayyidah Safiyyah (may Allah be pleased with her) said: "Pick up his head and throw it at those people, the ones who are below the fortress." He said: "By Allah! I cannot do this either." Sayyidah Safiyyah (may Allah be pleased with her) says: I took hold of that man's head and threw it towards those people. They said: "By Allah! We have come to know that Muhammad (peace and blessings be upon him) did not leave his family in such a state that there was no one with them." Then they scattered here and there and went away. Sayyidah Safiyyah (may Allah be pleased with her) narrates: Once the Prophet (peace and blessings be upon him) passed by Sayyiduna Sa'd bin Mu'adh (may Allah be pleased with him), who had a trace of yellow on him, as if he had been married a short while before, and he was reciting this verse: "In a little while the camel will reach the battle; there is no harm in death when the appointed time has come."
Al-Tabarani recorded it in al-Mu'jam al-Kabir and al-Mu'jam al-Awsat, through Umm Urwah bint Ja'far bin al-Zubayr from her father, and I do not know either of them. The rest of its narrators are thiqat (trustworthy).