Yahya bin Sa'id (may Allah have mercy on him) says that Abu Bakr al-Siddiq (may Allah be pleased with him) sent armies towards Syria. He mentioned the hadith about his instructions, at the end of which is: "A goat or a camel is to be slaughtered only for food."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18131