Sayyiduna Abdullah bin al-Zubayr (may Allah be pleased with them both) said: "On the day of (the Battle of) the Trench, I and Sayyiduna Umar bin Abi Salamah (may Allah be pleased with him) were with the women in the fortress of Hassan (bin Thabit). Sometimes he would bend down for me and I would look (out from above), and sometimes I would bend down for him and he would look."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8238