Reference for Sanhedrin 156:12
תניא אידך אמדוהו למיתה אומדין אותו לחיים לחיים אין אומדין אותו למיתה אמדוהו למיתה והקל ממה שהיה אומדין אותו אומד שני לממון ואם לאחר כן הכביד ומת משלם נזק וצער ליורשים
Now, on R. Nehemiah's view, it is right that two phrases bearing on judicial assessment are written;<span class="x" onmousemove="('comment',' V. Ex. XXI, 18f: And if men strive together, and one smite another with a stone, or with his fist, and he die not, but keepeth his bed: If he rise again, and walk abroad upon his staff, then shall he that smote him be quit: only he shall pay for the loss of his time, and shall cause him to be thoroughly healed. Two phrases are superfluous, viz., 'and he die not', and 'If he rise again and walk abroad upon his staff', for it is self-evident that the assailant cannot be executed under such circumstances: hence they must refer to a judicial calculation that he would not die, which was, however, subsequently falsified. ');"><sup>11</sup></span>