Praise be to Allah.
The shar’i evidence indicates that what is acceptable in the case of sheep is that which has reached the age of six months; in the case of goats it is that which has reached the age of one year; in the case of cattle it is that which has reached the age of two years; and in the case of camels it is that which has reached the age of five years. Anything younger than that is not acceptable as a hadiy or udhiyah. This is what is meant by “a Hady such as you can afford,” because the texts from the Qur'aan and Sunnah explain one another.
And Allah is the source of strength; may Allah send blessings and peace upon our Prophet Muhammad and his family and Companions. End quote.
Standing Committee for Academic Research and Issuing Fatwas.
Shaykh ‘Abd al-‘Azeez ibn ‘Abd-Allaah ibn Baaz, Shaykh ‘Abd al-Razzaaq ‘Afeefi, Shaykh ‘Abd-Allaah ibn Ghadyaan, Shaykh ‘Abd-Allaah ibn Qa’ood
Fataawa al-Lajnah al-Daa’imah, 11/376