Commentary for Bava Batra 63:6
דתניא לעולם אין עדותן מצטרפת עד שיראו שניהן כאחד ר' יהושע בן קרחה אומר אפילו בזה אחר זה אין עדותן מתקיימת בבית דין עד שיעידו שניהם כאחד ר' נתן אומר שומעין דבריו של זה היום ולכשיבא חבירו למחר שומעין דבריו:
and the point at issue here is whether the evidence [of different witnesses] can be combined, a point on which we find a difference between Tannaim. For it has been taught: 'The evidence of the two witnesses is not combined, and does not carry weight unless they both [testify to] have seen at the same time. R. Joshua b. Korhah, however, says that the evidence is combined even if one [testifies that he] saw at one time and the other at another.<span class="x" onmousemove="('comment',' E.g., one testifies that he saw the claimant lend the defendant a certain sum on one day, while the other maintains that it was on the next day. This first clause of the Baraitha here quoted has nothing to do with the argument, and is only inserted to make the quotation complete. ');"><sup>6</sup></span>