פירוש על מכות 3:4

לוקה ואינו משלם – for Rabbi Yehuda holds that (Deuteronomy 22:7) "שלח תשלח" /”Let [the mother] go” is implied from the outset, and even though, it is written,” let [the mother] go” after (verse 6) “do not take [the mother together with the young],” it is not to say that if you took it, you should let it go, but rather, do not take [the mother] but send her prior to the taking. And this is not a prohibitive law the transgression of which must be repaired by a succeeding [positive] act.

If one takes the mother bird with the young (Deuteronomy 22:6-7): Rabbi Judah says he is flogged and need not [then] send the mother free; But the Sages say: “He lets the mother go and is not flogged.”
This is the general principle; any negative commandment which involves a positive deed, one is not liable (for transgressing over.
Mishnah four discusses the prohibition of taking a mother bird with her young.
The last section of the mishnah states the principle that will explain the Sages’ position in the previous section as well as the last section of the previous mishnah. According to the mishnah any negative commandment which can be immediately remedied by a positive deed is not punishable by lashing. Our two mishnayoth illustrate commandments of this nature. Deuteronomy 22:6-7 states: “Do not take the mother (bird) with the young, Let the mother go”. The Sages understand the first half of this statement to be a negative commandment and the second half a positive deed which would remedy the violation of the negative commandment. In other words one who violates the negative commandment by taking the mother and the young can remedy it by doing a positive deed, namely by releasing the mother. Therefore, the Sages say that since he released the mother, he is not liable to be flogged.
Rabbi Judah reads the verse differently. He understands the second half to mean “Let the mother go” before you take her and the young. Once the person has taken the mother bird while the young are together with her in the nest he is immediately punishable by flogging, since he cannot remedy the situation. Since the commandment has already been violated and cannot be remedied, he is not obligated to release the mother bird.
This same general rule is also applicable with regards to the end of the previous mishnah which discussed leaving the Passover offering until morning. Exodus 12:10 states: “You shall not leave any of it until morning; if any of it is left until morning you shall burn it.” Again the first half of the verse is a negative commandment and the second half contains a remedy to the violation of that commandment. Therefore one who violates the prohibition of leaving the sacrifice until morning is not flogged.

וחכמים אומרים משלח ואינו לוקה – for they hold, “let [the mother] go” after taking, is implied, and it is a prohibitive law the transgression of which must be repaired by a succeeding act. And the Halakha is according to the Sages.

כל מצוה לא תעשה ישי בה קום עשה – for the Torah stated, if you transgressed on the negative commandment, fulfill the positive commandment, such as (Deuteronomy 22:6): “Do not take the mother together with her young.” But if you took it, “let [the mother] go” (verse 7); [and another example] (Deuteronomy 24:10): “[When you make a loan of any sort to your countryman], you must not enter his house to seize his pledge.” But if you seized his pledge, “you must restore the pledge to him” (verse 13). All of these, if he fulfilled the positive commandment, he is not flogged. But if he did not fulfill the positive commandment, such as the case where he took the mother [animal] with her young and slaughtered it or it died, or he took the pledge from his house (i.e. the home of the person who had borrowed something) and it was burned and he cannot fulfill the positive commandment, behold, that person is flogged.