It is narrated from Imam Ma'mar (may Allah have mercy on him) that he asked Imam al-Zuhri (may Allah have mercy on him): "Who wrote the treaty on that day (that is, on the occasion of the Treaty of al-Hudaybiyah)?" He laughed and said: "It was Sayyiduna Ali (may Allah be pleased with him); and if you were to ask those people, that is, Banu Umayyah, they would certainly say that it was Sayyiduna Uthman (may Allah be pleased with him)."
This narration makes clear that the document of the Treaty of al-Hudaybiyah was written by Sayyiduna Ali (may Allah be pleased with him), while Imam al-Zuhri pointed out the political inclination of Banu Umayyah to attribute this important service to Sayyiduna Uthman (may Allah be pleased with him) for the sake of their family's merit.
Hadith Referenceالمطالب العالية بزوائد المسانيد الثمانية / كتاب السيرة والمغازي / 4287
Hadith Gradingمحدثین:إسناده حسن، مرسل
Hadith Takhrij«حکم الحدیث المطالب العالیہ محققاً تنسیق د. سعد بن ناصر بن عبد العزيز الشَّثري- مکتبہ شاملہ :مرسل، إسناده حسن لغيره. » «انفرد به المصنف من هذا الطريق»