Hullin, Chapter Twelve, Mishnah Four
1) If one took the mother with the young:
a) Rabbi Judah says: he has incurred [forty] lashes and he need not now let her go.
b) But the sages say: he must let her go, and he does not incur lashes.
2) This is the general rule: [For the transgression of] any negative commandment which has of a remedy by the subsequent fulfillment of a positive commandment one does not incur lashes.
Section one: The Torah prohibits taking the mother bird, but then says that one should send the mother away. The question is: can one remedy the prohibition by performing the positive aspect of the commandment?
Rabbi Judah says that once he has taken the mother, he has irrevocably transgressed the commandment. There are two implications: 1) he has incurred the punishment for transgressing a negative commandment (lashes); 2) he need not send the mother away, because there is no longer any commandment to do so.
The other sages disagree. They hold that the transgression may be fixed by sending the mother away. Since when he transgresses there is the potential to fix the problem, one can never incur a punishment for transgressing such a type of commandment.
Section two: This is the general rule. If there is a negative commandment that can be remedied by performing a positive commandment, then one cannot receive lashes for transgressing the negative commandment.