Reference for Shabbat 45:9

והא יו"ט שני דספק דבריהם הוא ובעי ברכה התם כי היכי דלא לזילזולי בה רבא אמר רוב עמי הארץ מעשרין הן:

requires a benediction, whereas a doubtful Rabbinical law does not.<span class="x" onmousemove="('comment',' The kindling of light is a definite and certain observance; the tithing of dem'ai, however, is done through doubt. ');">²⁹</span> But what of the second day of Festivals, which is a Rabbinical [institution] based on doubt,<span class="x" onmousemove="('comment',' Scripture ordained Festivals of one day only at the beginning and end (viz., Passover and Tabernacles, v. Lev. XXIII, 7f, 35f) or one day altogether (Pentecost and New Year; ibid. 21, 24). The exact days when these were to be observed depended upon New Moon of the month in which they fell (except Pentecost), which was originally determined by direct observation, not by calculation. By experience it was found that New Moon was always either twenty-nine or thirty days after the previous New Moon, and as soon as it was thus fixed by the Great Court in Jerusalem, envoys were dispatched to inform the communities in time for the Festival. But they could not reach the Jewish communities outside Palestine in time, and therefore they observed two days instead of one. Thus the original reason of the added second day at the beginning and the end was on account of doubt, though it was retained even when the New Moon came to be determined by calculation, which precluded doubt. ');">³⁰</span> and yet it requires a benediction?<span class="x" onmousemove="('comment',' Viz. 'sanctification of the Festival', which was done by means of a benediction. ');">³¹</span> — There it [was instituted] in order that it should not be treated slightingly.<span class="x" onmousemove="('comment',' Unless the second day was formally sanctified people would not treat it as holy. ');">³²</span>

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