Mughirah bin Hadhf al-Absi said: We were with Sayyiduna Ali (may Allah be pleased with him) in al-Rahbah when a man from Hamdan came driving a cow along with its calf, and he said: I bought it to sacrifice it, and it has given birth. He said: Do not drink of its milk except what is left over from its calf, and when the day of sacrifice comes, slaughter it and its calf on behalf of seven (people).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19192