Reference for Chullin 281:42
בעלמא סבר לאו שניתק לעשה אין לוקין עליו והכא היינו טעמא משום דקסבר שלח מעיקרא משמע
<big><b>GEMARA: </b></big>R'Abba B'Memel raised the question: Is the reason for R'Judah's view [in the Mishnah] that he is of the opinion that [for the transgression of] a negative precept which can be remedied by a subsequent act [of the transgressor] one incurs stripes, or is it that elsewhere he is of the opinion that [for the transgressi of] a negative precept which can be remedied by a subsequent act one does not incur stripes, but here the reason is that he maintains that the precept of letting [the dam] go was intended only in the first instance?<span class="x" onmousemove="('comment',' And therefore once the dam has been taken both the negative and positive precepts have been infringed, and one is no longer obliged to send it away. V. p. 816, n. 3.');"><sup>31</sup></span>