Commentaire sur Le Deutéronome 15:19

כל הבכור ... תקדיש ALL THE FIRSTLING MALES … THOU SHALT SANCTIFY [UNTO THE LORD] — But in another passage (Leviticus 27:26) it states, “[Only the firstborn of the beasts …] one shall not sanctify it”? How can these be reconciled? The latter passage means: he must not dedicate it as a different sacrifice (i.e. offer it as an עולה or שלמים instead of as a בכור), whilst here it teaches that it is a duty to say: “Thou art holy as a firstborn!” Another comment is: It is impossible to say that “thou shalt sanctify” is to be taken literally, for it already states in another passage “one shall not sanctify it”; it is, on the other hand, also impossible to take “one shall not sanctify it” literally, since it states “thou shalt sanctify it”. How can these be reconciled? In the following manner: by taking תקדיש in our verse to imply: “thou mayest dedicate” so far as the dedication of its value (הקדש עלוי) is concerned, and then he must give a sum corresponding to the טובת הנאה in it to the Temple treasury, but you must not dedicate it as far as the altar is concerned (i.e. dedicate it as any sacrifice other than as a בכור) (Arakhin 29a: cf. Sifrei Devarim 124:4).

כל הבכור, after the Torah has listed a number of acts of kindness you are to perform with parts of your harvest in the field and orchard, something called the “tithe for the poor,” as well as an equivalent at the end of the sh’mittah year in money, i.e. the waiving of past due debts, acts of charity, and acts of helping your former servant to establish an economic base for himself, Moses now explains in detail commandments which are acts of gratitude vis a vis G’d, i.e. the giving to G’d or His representative the firstborn males of your livestock, i.e. sheep, goats and cattle. It is incumbent upon the owner of such herds to thank the Lord, for it is He Who is the source of his wealth. This is followed by repetition of the commandments to observe Passover, the commemoration of our obtaining political freedom, as well as the annual date on which the early barley harvest is acknowledged with an appropriate offering, and of Shavuot, the obtaining of our spiritual freedom when we received the Torah in capsule form, i.e. the Ten Commandments. Shavuot also ranks as the primary harvest festival celebrating the cutting of the wheat harvest.
Finally, we observe the Sukkot festival signaling that the last of the various harvests, particularly that of the trees has been successfully brought into the barns. On each of these festivals the farmer brings a gift for G’d with him when he makes the pilgrimage to Jerusalem and the Temple. This is spelled out in 16,16. Seeing that the occasion for this is one or all of these three festivals, there is no need for the Torah to mention a specific date as we all know the dates of these festivals. The Torah does mention the season during which these festivals occur, to remind us that they are connected with times of significance to each farmer.

תקדיש לה' אלוקיך, this means that you are to treat it as if sacred, i.e. not to shear its wool, not to use it to perform labour, etc. I have already explained the meaning of the words לא יקדיש איש אותו in Leviticus 27,26 as meaning that it cannot be designated as an offering for the altar.