Reference for Bava Batra 113:2
סבר רבינא למימר היינו מתניתין ג' אחין ואחד מצטרף עמהן
Said R. Ashi to him: Surely the cases are not on all fours. In that case [if the evidence of the brothers was accepted] three-quarters of the money would not be assigned on the evidence of brothers, but in this case [if we allow this man to testify] three-quarters of the money will be assigned on the evidence of brothers.<span class="x" onmousemove="('comment',' Each of the two original witnesses is regarded as warranting the assignment of half the money to the holder of the bond. Consequently, each of the witnesses to the dead man's signature is regarded as warranting the assignment of a quarter of the money. Hence three-quarters of the money is assigned on the warrant of two brothers who by rights ought not to count as more than a single witness. ');"><sup>2</sup></span>