Sayyiduna Abu Ayyub (may Allah be pleased with him) says: We lived with our Prophet (peace and blessings be upon him) while each household would sacrifice a single sheep; then a man sacrificed two sheep, and after that it became a matter of boasting and vying with one another.
Hadith Referenceالمعجم الكبير للطبراني / باب الخاء / 3966