Kedoshim: Chapter 21
"All its fruit shall be holy for praisegiving to Hashem"

Rabbi Chiya talks about the concept of fruits that are brought forth only from another force above, and that do not become ripened until three years have passed. In the fourth year, "all its fruit shall be holy for giving praise." The secret meaning of this is that in the fourth year the Congregation of Yisrael is paired with God, and there is praise and joy; the "fourth year" is God Himself and it is also the Congregation of Yisrael. Then the hosts are appointed over the world in their proper place, and everyone is blessed, and the fruits are now in perfection so may now be eaten. Until this point it is forbidden to eat of the fruits.