Reference for Bava Metzia 60:12
אמר מר (אשר) ילכו זה ביקור חולים היינו גמילות חסדים לא נצרכה אלא לבן גילו דאמר מר בן גילו נוטל אחד מששים בחליו ואפי' הכי מבעי ליה למיזל לגביה
Rabbah said: If he [the old man] smote it [the lost animal], he is [henceforth] under an obligation in respect thereof.<span class="x" onmousemove="('comment',' To return it. By smiting it to make it go in a certain direction he commences the work of returning it, and therefore must complete it. ');"><sup>3</sup></span> Abaye was sitting before Rabbah when he saw some [lost] goats standing. whereupon he took a clod and threw it at them. Said he [Rabbah] to him, 'You have thereby become bound in respect of them. Arise and return them.' The scholars propounded: What if it is dignified for one to return [a lost animal] in the field, but not in town? Do we say, a complete return is required, and since it is undignified for him to return it in town, he has no obligation at all; or perhaps, in the field at least he is bound to return it, and since he incurs the obligation in the field, he is likewise obligated in town?<span class="x" onmousemove="('comment',' On the principle of the preceding dictum. ');"><sup>4</sup></span>