Reference for Pesachim 186:17
אמר ליה לא לדידי קשיא ולא לרב יהודה קשיא לדידי ל"ק דרך רחוקה לטהור ואין דרך רחוקה לטמא
The [above] text [stated]: ''Ulla said, what is "a journey afar off"? Any place whence a man Is unable to enter [Jerusalem] at the time of slaughtering.' But Rab Judah maintained: Any place whence one is unable to enter [Jerusalem] at the time of eating. Rabbah said to 'Ulla: on your view there is a difficulty, and on Rab judah's view there is a difficulty. On your view there is a difficulty, for you say, 'Any place whence a man is unable to enter at the time of slaughtering': yet surely a man unclean through a reptile is unable to enter<span class="x" onmousemove="('comment',' Sc. the Temple.');"><sup>17</sup></span> at the time of slaughtering, yet you say, One slaughters and sprinkles on behalf of a person unclean through a reptile? On Rab Judah's view there is a difficulty, for he says, 'Any place whence one is unable to enter at the time of eating': but surely he who is unclean through a reptile is able to enter at the time of eating, yet he says, One may not slaughter and sprinkle on behalf of a man unclean through a reptile?<span class="x" onmousemove="('comment',' For this controversy v. supra 90b.');"><sup>18</sup></span> Said he to him: Neither on my view nor on Rab Judah's view Is there a difficulty. On my view there is no difficulty: 'A journey afar off' [is stated] in reference to a clean person, but 'a journey afar off' is not [stated] in refere an unclean person.<span class="x" onmousemove="('comment',' V. Num. IX, 13: But the man that is clean, and is not in a journey, and forbeareth to keep (lit., 'do') the Passover etc. From this we see, (i) that the exemption for a man who is in a 'journey afar off' applies to a clean person, and (ii) that a 'journey (afar off) ' is determined by his inability to do the Passover, i.e., to slaughter it. Hence if he is so far away that he cannot reach the Temple Court in time for the slaughtering, he is in a journey afar off'. But an unclean person is exempt because of his uncleanness, which prevents his eating, but not his sacrificing, since that can be done by another acting on his behalf. Moreover, since Scripture specifies one who is 'unclean by reason of a dead body' and does not state one who is unclean through a reptile, it follows that this exemption applies only to such as the former, who are unclean for a long period (seven days) and cannot be fit in the evening, but not to such as the latter, who can be fit to eat in the evening.');"><sup>19</sup></span>