Midrash for Pesachim 189:10
ואין לי אלא מצות עשה מצות ל"ת מנין ת"ל (במדבר ט, יב) לא ישאירו ממנו עד בקר
Our Rabbis taught: 'According to all the statute of the Passover they shall keep it': you might think, just as the first is subject to the prohibition of [leaven] 'shall not be seen' and 'shall not be found', so is the second subject to the prohibition of [leaven] shall not be seen and shall not be found: therefore it is stated, they shall eat it with unleavened bread and bitter herbs.<span class="x" onmousemove="('comment',' V. p. 508. they are alike only in respect of the regulations pertaining to or connected with itself, just like the particular case which is stated.');"><sup>13</sup></span> Again, I know it only of positive precepts;<span class="x" onmousemove="('comment',' 'They shall eat it' etc. is a positive precept, and therefore teaches that all the positive precepts applicable to the first Passover are also binding upon the second, e.g., the precept to eat it roast.');"><sup>14</sup></span>