In Exodus and Leviticus the age of certain sacrificial animals is specified as one year. Such as in Exodus 12:5. Why is it essential for the animal to be this age?
Rabbi Kook z"l writes in his book "Olat Ra'aya" That the Korban Hatamid, the daily sacrifice expresses the constant connection between the nation of Israel and Hashem. This is why this sacrifice is one year old to show the complete connection between us like a one year old animal which is completely innocent and did not have time to to become engrossed in the world. Rabbi Yitzchak Grinblat