Musnad Ahmad 32:168

Abu Usamah narrated to us, from Sulayman ibn al-Mughirah, from Thabit, from Anas, who said: Abu Talhah came on the day of Hunayn, making the Messenger of Allah, peace and blessings of Allah be upon him, laugh, regarding Umm Sulaym. He said: "O Messenger of Allah, have you not seen Umm Sulaym? She has a dagger with her." The Messenger of Allah, peace and blessings of Allah be upon him, said to her: "What are you doing with it, O Umm Sulaym?" She said: "I intended that if any one of them approached me, I would stab him with it."