Reference for Yoma 124:9
טעמא דרבי רחמנא הא לא רבי רחמנא פסולות עכובא מנא לן סלקא דעתך אמינא תהיה כתיב
Now the reason is only that the Divine Law expressly includes it, but had the Divine Law not done so, one would have assumed that they are invalid, whence do we assume this indispensability? - You might have thought we say: It is written: [This] shall be [the law].<span class="x" onmousemove="('comment',' Ibid. 2. 'Shall be' implies precise instructions from which there may be no deviation.');"><sup>6</sup></span> But now that the Divine Law has said: 'Lamb', 'lamb', what purpose serves 'shall be'? - That refers to the rest of the status of the leper.<span class="x" onmousemove="('comment',' I.e., to the other regulations relating to the purification of the leper.');"><sup>7</sup></span>