It is narrated from Mujahid (may Allah have mercy on him) that the Messenger of Allah (peace and blessings be upon him) said: "A bequest is not permissible for an heir."
Al-Shafi'i said: Some of the people of Syria narrated a hadith that is not among what the people of hadith regard as established, because some of its narrators are unknown. So we have narrated it from the Prophet (peace and blessings be upon him) as munqati' (with a broken chain), and we have relied on the report of the people of the maghazi in general that the Prophet (peace and blessings be upon him) said in the year of the Conquest: "There is no bequest for an heir," together with the consensus of the generality (of scholars) on holding this view.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الوصايا / 12536