On the day of the Battle of the Trench, Umar bin Abu Salama and I were in the fortress where the wives of the Messenger of Allah ﷺ had taken shelter, the fortress of Hassan. He would lift me up and I would lift him up, and when he lifted me I could recognize my father as he passed by on his way to Banu Qurayza. He was fighting alongside the Messenger of Allah ﷺ on the day of the Trench, when the Prophet ﷺ asked, "Who will go to Banu Qurayza and fight them?"When my father returned, I said to him, "Father, by Allah, I could recognize you as you passed by on your way to Banu Qurayza."He replied, "My son, by Allah, the Messenger of Allah ﷺ would join both of his parents together as a ransom for me, saying, 'May my father and mother be your ransom.'"
حدثنا أبو أسامة أنبأنا هشام عن أبيه
لما كان يوم الخندق كنت أنا وعمر بن أبي سلمة في الأطم الذي فيه نساء رسول الله ﷺ أطم حسان فكان يرفعني وأرفعه فإذا رفعني عرفت أبي حين يمر إلى بني قريظة وكان يقاتل مع رسول الله ﷺ يوم الخندق فقال من يأتي بني قريظة فيقاتلهم فقلت له حين رجع يا أبت تالله إن كنت لأعرفك حين تمر ذاهبا إلى بني قريظة فقال يا بني أما والله إن كان رسول الله ﷺ ليجمع لي أبويه جميعا يفديني بهما يقول فداك أبي وأمي
Its isnad is sahih. Al-utum, with the vowel points on the alif and ta, means a raised structure like a fortress, and it is singular, its plural being aatam. The hadith was narrated by Bukhari 7:64–65, and it was also narrated by Muslim, Tirmidhi, and Ibn Majah, as noted in Dhakhair al-Mawarith 1886. Ibn Saad narrated it in abbreviated form, 74/1/3. It will come again at 1423. See also 1408.