And as for a place, the Prophet—may Allah bless him and grant him peace—said: “Do not turn my grave into a festival.”
The word “festival” (ʿīd) may also refer to the day together with the acts performed on it, and this is the prevailing usage, as in the Prophet’s statement, peace be upon him: “Leave them, O Abū Bakr, for every people has a festival, and this is our festival.”
Accordingly, when the Prophet—peace and blessings upon him—asked, “Does that site contain one of their festivals?” he meant: “Is there a customary gathering of theirs that is held there as a festival?” When the man replied, “No,” the Prophet said, “Fulfil your vow.”
This shows that the mere fact of the location being the venue of their festival prevents slaughtering there—even when one has made a vow—just as its being a place of their idols does. Otherwise the conversation would not be coherent, nor would the detailed questioning be meaningful.
It is clear that the rationale is either the veneration of that spot, because they exalt it by celebrating their festival there; or sharing with them in that celebration; or reviving the emblem of their festival there, and the like—for what is involved is nothing other than the place of the act, the act itself, or its time.
If the prohibition is due to designating the spot—and that is the most apparent reading—then the ban concerns specifying that place precisely because it was the locale of their festival. Hence, once it was free of that association, permission was given to slaughter there, even though the intention to specify the spot remained.
Thus it becomes clear that the objection lies in singling out the site of their festival; and if designating the site of their festival is objectionable, then how much more so the festival itself! Likewise, when the site was disapproved because it was the locus of their idolatry, that served as an even stronger indication of the prohibition of polytheism and idol-worship.