Muwatta Malik 888
موطأ مالك#888SahihThese are the words of a Successor — the generation after the Companions — not of the Prophet ﷺ.
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ هِشَامِ بْنِ عُرْوَةَ، أَنَّ أَبَاهُ، كَانَ يَنْحَرُ بُدْنَهُ قِيَامًا . قَالَ مَالِكٌ لاَ يَجُوزُ لأَحَدٍ أَنْ يَحْلِقَ رَأْسَهُ حَتَّى يَنْحَرَ هَدْيَهُ وَلاَ يَنْبَغِي لأَحَدٍ أَنْ يَنْحَرَ قَبْلَ الْفَجْرِ يَوْمَ النَّحْرِ وَإِنَّمَا الْعَمَلُ كُلُّهُ يَوْمَ النَّحْرِ الذَّبْحُ وَلُبْسُ الثِّيَابِ وَإِلْقَاءُ التَّفَثِ وَالْحِلاَقُ لاَ يَكُونُ شَىْءٌ مِنْ ذَلِكَ يُفْعَلُ قَبْلَ يَوْمِ النَّحْرِ .
Yahya related to me from Malik from Hisham ibn Urwa that his father used to kill his sacrificial animals while they were standing. Malik said, "No-one is permitted to shave his head until he has killed his sacrificial animal, and no-one must sacrifice before dawn on the day of sacrifice. The things that should be done on the day of sacrifice are slaughtering, donning clothes, grooming the body generally (at-tafath) and shaving the head, and none of this may be done before the day of sacrifice
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
In-book reference: 20:184