For that reason the Prophet ﷺ, during the Farewell Pilgrimage, paused so that the people could put their questions to him. A man said, “I was unaware and shaved before slaughtering.” He replied, “Slaughter, and there is no sin.” Another came and said, “I was unaware and slaughtered before casting the pebbles.” He said, “Cast the pebbles, and there is no sin.” The narrator adds: On that day he was not asked about anything that had been done earlier or later than its prescribed order except that he said, “Do it, and there is no sin,” a clear sign of this religion’s mercy and ease.

Points extracted from the ḥadith:

1. A scholar should make himself available during the days of the rites to issue legal opinions and guide the people concerning their pilgrimage.
2. For the one who forgets or is ignorant, it is permissible to perform the stoning, the sacrifice, the shaving or trimming, and the circumambulation in any order. The discussion regarding someone who alters the order deliberately will follow, God willing.
3. The Day of Sacrifice begins with casting the pebbles at Jamrat al-ʿAqabah. One of the wisdoms behind this stoning is to repel Satan; in that respect it resembles opening the prayer with seeking refuge from him. This comparison came to my mind, and I have not seen it mentioned by the scholars. Perhaps one of them has said it and I have not come across it. If it is correct, then it is from Allah; if it is mistaken, then it is from me.

Differences among the jurists:
The scholars unanimously agree that the prescribed order is to stone, then slaughter the sacrificial animal, then shave or trim the hair, and finally make the ṭawāf of ifāḍah, exactly as the Prophet ﷺ arranged them.
They differ, however, about the permissibility of changing this order intentionally.
Al-Shāfiʿī and the well-known view of Imam Aḥmad hold that it is permissible, citing the report recorded by the two Shaykhs (al-Bukhārī and Muslim) from ʿAbd Allah ibn ʿAmr: “Messenger of Allah, I shaved before slaughtering.” He answered, “Slaughter, and there is no sin.” Another said, “I slaughtered before casting the pebbles.” He replied, “Cast, and there is no sin.” This is one of the chains of transmission for the ḥadith under discussion, and in another wording: “He was not asked about anything that had been done earlier or later than its prescribed order except that he said, ‘Do it, and there is no sin.’”