Alqamah (may Allah have mercy on him) says that Abdullah bin Mas'ud (may Allah be pleased with him) sent a voluntary sacrificial animal with me and said: Eat, you and your companions, one third; give one third in charity; and send one third to the family of my brother Utbah. (That is, the meat of the sacrifice should be divided into three parts.) [Sahih. Recorded by al-Tabarani in al-Kabir: 9702]
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 10238