Tosefta for Bava Batra 156:8
אמר רבא חמורך זו ידע דחמרא דידיה הוא והאי דקא א"ל זו משום כליו קא"ל חמורך הוא דלא ידע דחמרא דידיה הוא והכי קא"ל חמורך הוא שתמכרנה לי:
[ITS] FOAL. HE WHO SOLD A COW HAS NOT SOLD ITS CALF [ALSO]. HE WHO SOLD A DUNGHILL HAS [ALSO] SOLD THE MANURE IN IT. HE WHO SOLD A CISTERN HAS [ALSO] SOLD ITS WATER. HE WHO SOLD A BEE-HIVE HAS [ALSO] SOLD THE BEES. HE WHO SOLD A DOVE-COTE HAS [ALSO] SOLD THE DOVES. <b><i>GEMARA</i></b>. Of what case [does the first part of the Mishnah speak]? If [it is] that the [seller] said unto him, '[I sell you] it and its young', then even [in the case of the] cow and its young the same [law should apply].<span class="x" onmousemove="('comment',' I.e., that the calf should he sold implicitly together with the cow. ');"><sup>21</sup></span> If, [however], he did not specify, 'it and its young', [then] even [in the case of the] ass also [the foal should] not [be included in the sale]? — R. Papa answered: [The Mishnah speaks of a case] where [the seller] said unto him, 'I sell you a milch-ass or a milch-cow'. [Consequently in the case of the] cow, it may properly be assumed [that the seller<span class="x" onmousemove="('comment',' Who mentioned 'milch'. ');"><sup>22</sup></span>