ל"ה - הלכות ערלה ד:ג
(Painting by Margarita Levine)
Once a person is able to subdue his three principle inclinations for sexual immorality, food, and money, which correspond to the three years of the orlah when the fruit of such a tree is forbidden to be eaten, he then merits the concept of rebuilding Yerushalayim. This relates to complete fear of God, which depends on one's heart. Therefore, after the first three years of orlah one must bring the first fruits to Yerushalayim, which are a concept of complete fear that a person merits because he cast away his evil urges. He succeeds to cast away his evil urges because he did not partake of the orlah fruit. And, by rebuilding Yerushalayim one merits tefilah. On the fourth year all of one's fruits "shall be holy and will give praise to Hashem." (Vayikra 19:24) "Holy and will give praise" refers specifically to prayer, which consists of praise to Hashem. A person merits prayer by helping to rebuild Yerushalayim and subduing his three main urges.