Commento su Deuteronomio 15:20

לפני ה׳ אלהיך תאכלנה THOU SHALT EAT IT BEFORE THE LORD THY GOD — Scripture is speaking to the priest (not to the owner to whom תקדיש in the previous verse refers), for we find already stated that it (the בכור) is one of the dues of the priests whether it is unblemished (and its blood and fat portions are to be sacrificed on the altar and the flesh eaten by the priests), or whether it is blemished (when it must not be offered on the altar), for it states, (Numbers 18:18) “and the flesh of them (the firstborn animals, both the blemished and the unblemished) shall be thine” (the priest’s) (cf. Bekhorot 28a).

בשעריך) תאכלנו), “you may consume it in your cities.” The Torah refers to people who are authorized to eat it (priests).
שנה בשנה, “year by year;” this does not mean that it is forbidden to eat it after it has attained its first birthday as it has been compared elsewhere to the second tithe (Deut. 14,23), but it means that preferably it is to be eaten before it has attained its first birthday.
אתה וביתך, “you and your house,” i.e. the household of the priest.

Just as the second tithe is not disqualified from one year to the next, etc. As it is written regarding the tithes (above 14:28), “At the end of three years, separate all the tithes of your produce,” and Rashi explains, “This comes to teach that if one withheld his tithes, etc.”

V. 20. לפני ד׳ אלדיך וגו׳ (Bamidbar 18, 18) ist בכור בהמה טהורה als מתנת כהנה dem כהן zum Genusse wie חזה ושוק של שלמים überwiesen (siehe daselbst). Hier wird noch die Bestimmung gegeben, dass es Mizwa sei, jeden בכור im ersten Jahre seiner Geburt durch Opferung und Genuss in der Gottesstadt seiner Bestimmung zuzuwenden. Diese bei בכור wie bei מעשר (Kap. 14, 22) ausgesprochene שנה בשנהBestimmung lässt den Boden- wie den Herdensegen eines jeden Jahres für sich als ein besonderes in sich abgeschlossenes Augenmerk der göttlichen Fürsorge beherzigen, wie es ja Kap. 11, 12 heißt: ארץ אשר וגו׳ תמיד וגו׳ מראשית השנה ועד אחרית השנה (siehe daselbst).

שנה בשנה [THOU SHALT EAT IT BEFORE THE LORD …] YEAR BY YEAR — From here we derive the law that one should not defer it (i.e. sacrificing and eating it) beyond its first year (Bekhorot 28a). If so, one might think that it becomes invalid as a sacrifice as soon as its first year has passed! This is not the case, for it has been put in comparison with the second tithe, as it is said, (Deuteronomy 14:23; cf. Rashi on that verse): “and thou shalt eat before the Lord thy God the tithe of thy corn, of thy wine, and of thine oil, and the firstlings of thy herds, and thy flocks”. How is it in the case of the second tithe? It does not become invalid if left over from one year to the other (cf. Rashi on Deuteronomy 14:28 and 29), so, too, does the firstborn animal not become invalid under the same circumstances, only that it is a meritorious act to offer and consume it within its first year.

אתה וביתך, wie נאכל לכהנים לנשיהם ולבניהם ולעבדיהם :חזה ושוק (Sebachim 55 a).

שנה בשנה (may also be translated A YEAR WITH ANOTHER YEAR) — If one slaughtered it at the end of its first year (an the last day) he may eat it that day and the first day of the next year. This teaches us that it (a firstborn animal) may in all cases be eaten on two successive days and the intervening night (cf. Sifrei Devarim 125; Bekhorot 27b).