Responsa for Moed Katan 6:11
דידהו היא הלכה למשה מסיני היא דאמר ר' אסי אמר ר' יוחנן משום ר' נחוניא איש בקעת בית חורתן עשר נטיעות ערבה וניסוך המים הלכה למשה מסיני
were 'halachah' of Moses from Sinai! - Said R'Isaac, When we received on tradition that law [of extra restriction] as [an ancient] halachah, It was only in reference to 'thirty days prior to the New Year'; thereafter came those [of Beth Shammai and Hillel] and instituted [the cessation] from Passover<span class="x" onmousemove="('comment',' For a 'white field', growing cereals and legumina.');"><sup>18</sup></span> and the Feast of Weeks,<span class="x" onmousemove="('comment',' For a tree field, an orchard.');"><sup>19</sup></span> and [at the same time] they stipulated with reference to their [measure] that whoever might [thereafter] wish to abrogate [them] might come and abrogate them.<span class="x" onmousemove="('comment',' And it is only these two earlier terms, Passover and Feast of Weeks, up to thirty days before New Year that Rabban Gamaliel and his Beth din abrogated. Cf. J. Sheb. I, 5.');"><sup>20</sup></span>