On the day of Hudaybiyyah, some men shaved their heads while others shortened their hair.The Messenger of Allah ﷺ said, "May Allah have mercy on those who shaved."They said, "Messenger of Allah, and those who shortened?"He said, "May Allah have mercy on those who shaved."They said, "Messenger of Allah, and those who shortened?"He said, "May Allah have mercy on those who shaved."They said, "Messenger of Allah, and those who shortened?"He said, "And those who shortened."They asked, "Messenger of Allah, why was your mercy directed to those who shaved in particular?"He replied, "They did not doubt."Then the Messenger of Allah ﷺ departed.
حلق رجال يوم الحديبية وقصر آخرون فقال رسول الله ﷺ: يرحم الله المحلقين قالوا: يا رسول الله والمقصرين؟ قال: يرحم الله المحلقين قالوا: يا رسول الله والمقصرين؟ قال: يرحم الله المحلقين قالوا: يا رسول الله والمقصرين؟ قال: والمقصرين. قالوا فما بال المحلقين يا رسول الله ظاهرت لهم الرحمة؟ قال: لم يشكوا قال: فانصرف رسول الله ﷺ.
Imam Ahmad narrated it (3311), and this is his wording, as did Tahawi in Sharh Maani al-Athar (4057), and Ibn Majah (3045) in abridged form, all of them from the hadith of Muhammad bin Ishaq, who said, "Abdullah bin Abu Najeeh narrated to me," from Mujahid, from Ibn Abbas, and he related it. Its chain is hasan because of Muhammad bin Ishaq, for he is a mudallis whose hadith is hasan when he states his source explicitly.As for his saying, "He showed them mercy openly," it means he gathered and repeated mercy for them. And as for his saying, "They were not treated with doubt," it means they were not treated in the manner of one who doubts the permissibility of ending the state of ihram, meaning that whoever shortened his hair may have appeared to doubt the permissibility of ending ihram, to the point that he limited his release from ihram to only part of it, whereas whoever shaved his head showed no doubt at all. That is, they were not treated in the manner of one who doubts that following the fuller practice is better. As for the one who shortened his hair, he was treated in the manner of one who doubts this, since he abandoned doing it fully ﷺ. This was stated by Sindi in his marginal notes on the Musnad.