Musar for Niddah 45:4
כל גזרה שוה שאינה מופנה כל עיקר למדין ומשיבין
in the name of R. Eleazar in the direction of leniency. From any <i>gezerah shawah</i> none of whose terms is available for deduction, one may make the deduction and one may also offer a refutation; if one of its terms only is available for the purpose, deduction, according to R. Ishmael, may be made and no refutation may be offered, while according to the Rabbis deduction may be made and a refutation may be offered; and if two of its terms are available for deduction, all agree that deduction may be made and no refutation may be offered. But according to the Rabbis<span class="x" onmousemove="('comment',' Who maintain that whether one, or none of the terms is available for deduction both deduction and refutation are admissible. ');"><sup>4</sup></span>