ʿAbdullāh b. ʿUmar once sacrificed an uḍḥiyah in Al-Madīnah. He told me to buy a horned ram for him, and then to slaughter it on the Day of Aḍḥā at the people’s prayer place (muṣallā), so I did that. Then it was taken to ʿAbdullāh b. ʿUmar, and he shaved his head once the ram was slaughtered. He was ill at the time and had not witnessed the ʿEid with the people.
And ʿAbdullāh b. ʿUmar used to say: “Shaving the head is not obligatory upon the one who sacrifices an uḍḥiyah.” But Ibn ʿUmar had himself done it.
Al-Imām Mālik, Al-Muwaṭṭā, Book of Sacrificial Slaughters, Chapter on What is Recommended of the Sacrifices.
It is reported that Al-Ḥasan (Al-Ḥasan Al-Baṣrī) used to shave his head on the Day of Naḥr (ʿEid Al-Aḍḥā) in Basra.
Ibn Abī Shaybah, Al-Muṣannaf no. 13893.
Ibn ʿAwn asked Muḥammad (Ibn Sīrīn), “Did they used to recommend that a man should take off some of his hair on the Day of Naḥr?” He replied, “Yes.”
Op. cit. 13894.