Reference for Chullin 269:6

שתי רחלות שנאמר (ישעיהו ז, כא) יחיה איש עגלת בקר ושתי צאן

BETH SHAMMAI SAY, [AT LEAST] TWO SHEEP, AS IT IS SAID, A MAN SHALL REAR A YOUNG COW AND TWO SHEEP.<span class="x" onmousemove="('comment',' Isa. VII, 21. The term 'flock' stated in connection with the law of the first of the fleece is in this verse used of two sheep. ,uhuag vag');"><sup>3</sup></span>