<span class="x" onmousemove="Show('perush','Este es el <b>79no Precepto Positivo</b> enumerado por el Rambam en el Prefacio a Mishné Torá, su “Compendio de la Ley Hebrea” para todo el Pueblo de Israel.',event);" onmouseout="Close();">Santificarás al Señor, tu Dios, todo primogénito macho que nacerá</span>; de tus vacas y de tus ovejas: <span class="x" onmousemove="Show('perush','Este es el <b>113er Precepto Negativo</b> enumerado por el Rambam en el Prefacio a Mishné Torá, su “Compendio de la Ley Hebrea” para todo el Pueblo de Israel.',event);" onmouseout="Close();">no te sirvas del primogénito de tus vacas</span>, ni <span class="x" onmousemove="Show('perush','Este es el <b>114to Precepto Negativo</b> enumerado por el Rambam en el Prefacio a Mishné Torá, su “Compendio de la Ley Hebrea” para todo el Pueblo de Israel.',event);" onmouseout="Close();">trasquiles el primerizo de tus ovejas</span>.
Rashi
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, “all the firstling males, etc.;” this paragraph has been written here seeing that previously the Torah dealt with the rules governing the treatment of a Jewish “slave,” i.e. someone employed by a fellow Jew not of his free choice, and not free to leave such employment at will. Here, in verse 19, the Torah imposes restrictions on how the owner of an animal is not free to treat such an animal as if it did not possess any rights, i.e. לא תעבוד בבכור שורך, “you shall not make the firstborn of your ox perform menial labour.” Not only that, but the Torah has repeated this legislation in order to teach us that a blemished firstling animal must not even be offered as a sacrifice to G-d.
The common theme which connects the passage of all the firstling males to the previous passage is you must not do any work with the firstlings of your ox.
לא תעבד בבכור שורך ולא תגז וגו׳ THOU SHALT NOT WORK WITH THE FIRSTLING OF THY HERD, NOR SHEAR [THE FIRSTLING OF THY FLOCK] — The converse case also (working with the firstborn sheep and using the hair of the firstborn calf) have our Rabbis derived to be forbidden, but Scripture merely speaks of what usually occurs (Sifrei Devarim 124:6; Bekhorot 25a).