Reference for Pesachim 9:3

ואכילת חמץ לאכילת מצה דכתיב (שמות יב, כ) כל מחמצת לא תאכלו בכל מושבותיכם תאכלו מצות (וגו') וכתיב ביה במצה (שמות יב, יח) בערב תאכלו מצות

and in respect to unleavened bread it is written, at even ye shall eat unleavened bread.<span class="x" onmousemove="('comment',' Ibid. 18. Hence no verse would be necessary to show that as soon as evening commences the leaven must be put away; therefore the verse quoted supra can only refer to the fourteenth.');">⁴</span> Yet perhaps it is to include the night of fourteenth [as the time] for removal?<span class="x" onmousemove="('comment',' Since we see that leaven is to be removed on the fourteenth, perhaps it must be done at the beginning of the fourteenth, Sc. in the evening.');">⁵</span>

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