Is it permissible for an Uḍḥiyah to be offered on behalf of the deceased who did not bequeath it, especially if he was 18 years old?

If the deceased made a bequest for a sacrifice (udhiyah) on their behalf, or established an endowment (waqf) for it, then this is permissible by consensus. If it was an obligatory (wajib) sacrifice, then their heirs are obligated to fulfill it. However, if the deceased did not make such a bequest, scholars have differed.

The Shafi'is hold that it is not permissible unless there is a bequest or an endowment. In contrast, the Hanbalis, Hanafis, and Shaykh al-Islam Ibn Taymiyyah are of the view that it is permissible.

As for the Malikis, they disliked sacrificing on behalf of the deceased if there was no bequest. Imam Malik said, "It does not please me for one to sacrifice on behalf of his deceased parents," because it was not reported from the Prophet (peace be upon him) nor from any of the early Muslims (Salaf), and often the intention behind it is ostentation. The hadith narrated by Ali (may Allah be pleased with him) about his sacrificing two rams on behalf of the Prophet (peace be upon him) is weak due to the unknown reliability (jahalah) of Abu al-Hasna'.