The Mishnah here is going to talk about the idea of a lav hanitak la'aseh: if a person has a negative commandment that he violated and there's a positive commandment that could fix it up, there would be no Malkot (lashes) in that situation. We'll talk about it in the context of the mitzvah (commandment) of shooing away a mother bird before taking the eggs. As the Pasuk (verse) tells us, if you see that situation, don't take the mother with the young. Send away the mother, and then take the eggs that are there. The question becomes: how do you read this Pasuk? Is it that if a person didn't send them away and then took the eggs, he violated the prohibition, and there's no fix? Or, if he did wrong by taking the mother with the young, with the eggs, then shaleach teshalach: if you send away the mother, then that's sort of an aseh. That's a positive commandment that fixes up the problem that a person made.
We'll have a machloket (dispute) between Rabbi Yehudah and Chachamim (Sages) about that. The Mishnah says: If a person takes a mother bird while she's with her young bird or eggs, Rabbi Yehudah says he gets Malkot and he doesn't have to do anything to send the mother bird away. Once he made the aveirah (violation) and took the mother while she was with her eggs, he no longer has the mitzvah to send the mother away. It's a one-time opportunity. It's not a lav hanitak la'aseh. There's no negative followed by a positive fix-up over here. It's not a lav hanitak la'aseh. There's no fixing that situation.
But Chachamim disagree. They say that even though a person already violated the prohibition of taking the mother with the eggs, he has to send away the mother bird. If he sends away the mother bird at that time, even after he already took the eggs, he has fixed up the problem and would not receive Malkot for having taken the mother while she was with the eggs. Chachamim are going to explain their ruling based on how they understand the Torah prohibition. This is the general rule: for any prohibition that has a positive mitzvah to correct it, the Torah gives you a commandment afterward; if you violated that prohibition, ve'ein chayavin: a person would not be liable for Malkot for violating that prohibition. By doing that aseh, by doing that commandment, you fixed up the lo ta'aseh (negative commandment) that you would have received Malkot for. So here, even though the Torah tells you, “Don't take the mother bird with her young,” it says afterward that you have to send away the mother bird. So according to Chachamim, every person who violates it and takes the mother when she's with her young, if he just sends away the mother afterward, has fixed up the violation he committed, and he is not given Malkot.