Reference for Rosh Hashanah 41:3
מכריז ר' יוחנן כל היכא דמטו שלוחי ניסן ולא מטו שלוחי תשרי ליעבדו תרי יומי גזירה ניסן אטו תשרי
R'Johanan issued a proclamation: 'In all those places which can be reached by the messengers sent out in Nisan but not by those sent out in Tishri,<span class="x" onmousemove="('comment',' The messengers sent out from Jerusalem to announce the New Moon of Nisan would be able to travel further by Passover than the messengers sent out in Tishri would be able to travel by Tabernacles, because the latter would lose two days on New Year and the Day of Atonement, when it was forbidden to travel.');"><sup>6</sup></span> two days should be kept [on Passover],<span class="x" onmousemove="('comment',' Although the inhabitants would know when the New Moon of Nisan had been proclaimed.');"><sup>7</sup></span> Nisan being included so that there should be no mistake as to Tishri'.<span class="x" onmousemove="('comment',' I.e., if they kept Passover only one day, they might come to keep Tabernacles only one day.');"><sup>8</sup></span>