Mughira and Ibrahim, may Allah have mercy on them, said: If two among the heirs bear witness (regarding a debt or a bequest upon the deceased), then it will be permissible for all the heirs; and if only one heir bears witness, then the payment (of that debt or bequest) will be from his own share and portion.
Hadith Referenceسنن دارمي / من كتاب الوصايا / 3254