Leviticus 19:23

And when you have come into the land, and have planted any tree that may be eaten of, you shall verily circumcise the fruit of it; three years shall it be to you for rejection, to be destroyed; it shall not be eaten.

Having mentioned the sowing of crops [:19], and the sowing of a woman [:20] (who is analogous to the soil), Scripture proceeds to things that are planted, and discusses the forbidden fruits. It is well known that fruit which grows on trees less than three years old is harmful and contains no nutrition (just as fish that do not have fins and scales are harmful, and meat from birds of prey and from the non-kosher beasts is detrimental to the intelligence — verbum sat sapienti ).

you will leave its fruit unused [literally: you shall regard the fruit as uncircumcised] You shall treat it as you treat a foreskin, which is harmful and serves no purpose (linguistically, a foreskin [Hebrew: ‘orla] is an “impediment” of the flesh, like a speech impediment [Hebrew: ‘orla], or a hearing impediment [Hebrew: ‘orla]).

unused Literally means to treat something as an ‘orla ; but the Aramaic translation is also worthy of note [“You shall put it aside for destruction”].

it will be forbidden as a consequence of having regarded it as uncircumcised.

VA’ARALTEM ORLATHO’ THE FRUIT THEREOF. “[This means literally]: ‘ye shall close its closing,’ meaning that it shall be closed up and hidden so as not to have any benefit from it.” This is Rashi’s language, and he has explained it well. And if so, ‘erel’ of heart means “closed of heart,”. just as it is said, and I will rend the enclosure of their heart. Similarly, ‘areila’ is their ear means “their ear is closed and dulled so that no sound enters therein.” And ‘aral’ of the lips means “closed of lips,” for defective speech is a result of an impediment and obstruction in the veins of the tongue, or sometimes in those of the lips, which have not been properly opened. Speech is referred to in Scripture by the term “opening,” thus: Open thy mouth for the dumb [which means, “speak up in the cause of the dumb”]; Job opened his mouth; and the opening of my lips shall be right things; keep the doors [literally: “openings”] of thy mouth from her that lieth in thy bosom. Now Scripture uses the expression “closing up” with reference to the fruit of the first three years, so as to prohibit the deriving of any benefit from it, although it does not express it in this way with reference to other things from which we are also forbidden to derive any benefit [e.g., diverse kinds in a vineyard]. This is because the appearance of the fruit in its earliest stage is called “opening,” just as it is said, the vine-blossom has opened. Therefore He said, three years shall it be ‘areilim’ unto you, as if the fruits are closed up in the trees, and have not put forth buds nor opened blossoms.
The reason for this commandment is to honor the Eternal with the first of all our produce of the fruits of the tree and the increase of the vineyard, and that we are not to eat of them until we bring all the fruit of one year [i.e., the fourth year after the planting] for giving praise unto the Eternal. Now the fruit of the first three years is not fit to be brought before the Glorious Name because it is small; neither does the tree in its first three years impart good taste or flavor into its fruit. Besides, most trees do not bring forth fruit at all until the fourth year. Therefore we are to wait with all of them [an equal period of time], and are not to taste of their fruit until we have brought of the planting which we have done, all its first good fruit to be holy before G-d, and there [in …

וערלתם, you will treat it as totally out of bounds, keeping your distance from it. The word occurs in a similar sense both in Jeremiah 6,10 ערלה אזנם, referring to the people’s ears, and in Ezekiel 44,9 ערל לב, describing the heart as totally unapproachable. We also find it in a similar sense in Chabakuk 2,16 שתה גם אתה והערל, where it also denotes someone utterly disgraced.

וערלתם, the expression ערלה basically describes an infant, which during the first three years of its life is totally illiterate. After that it begins to learn to speak intelligently; in other words, it produces some “fruit,” during that year, and during the next year it learns how to read and write, i.e. to understand parts of the Torah. Subsequently such youngsters begin to make contributions to civilised society. (Compare Talmud, tractate Baba Batra folio 21, where a youngster is described as having to study Torah from the age of six as he is mature enough). Compare also Ethics of our Fathers chapter 5 Mishnah 21 where a youngster of five years is described as ready to study the written text of the Torah.