Reference for Pesachim 134:4

ומאי חומריה כדאמרן אדרבה בעל קרי חמור שכן מטמא במשהו

days, but only until evening, while a reptile too defiles until evening only, think, if zabin and lepers forced their way through and entered the Temple Court at a Passover sacrifice which came in uncleanness, - you might think that they are culpable; therefore it is stated, ['Command the children of Israel,] that they send out of the camp every leper', and every one that hath an issue [zab], and whosoever is unclean by the dead': when those who are unclean by the dead are sent out, zabin and lepers are sent out; when those who are unclean by the dead are not sent out, zabin and lepers are not sent out.

Jastrow