I asked Abu Ayub al-Ansari how the sacrifices were during the time of the Messenger of Allah ﷺ. He replied, "A man would sacrifice a single sheep on behalf of himself and his household. They would eat from it and feed others, until people began to compete in showing off, and it became as you now see."
حدثني يحيى بن موسى حدثنا أبو بكر الحنفي حدثنا الضحاك بن عثمان حدثني عمارة بن عبد الله قال سمعت
سألت أبا أيوب الأنصاري كيف كانت الضحايا على عهد رسول الله ﷺ فقال كان الرجل يضحي بالشاة عنه وعن أهل بيته فيأكلون ويطعمون حتى تباهى الناس فصارت كما ترى
[Sahih] Ibn Majah also narrated it in the Book of Sacrifices, chapter, "Sacrificing a single sheep on behalf of one's household," hadith 3147, from the hadith of Dahhak bin Uthman with the same wording. Also see the hadith of Malik in Muwatta (Pakistani edition), p. 497, and Bayhaqi, 9/268.