תּלמוד אויף במדבר 5:3

And an impure person who ate sacrificial food: [Receiving malkus by] enters the Temple while impure is understandable as both the punishment and the scriptural warning are written in the Torah. The punishment is written (Numbers 19,13) "The Tabernacle of G-d he has defiled and he shall be cut off". The scriptural warning is written (Numbers 5,3) "And he shall not defile the camps". But as for an impure person who ate sacrificial [meats] the punishment is easily understandable as it is written (Leviticus 7,20) "And the soul that eats meat from the alter of the Sh'lamim that are for G-d while his impureness is upon him will be cut off", only from where is the scriptual warning derived?

They asked him [Rebbi Yochanon] Did you say this? [that any prohibition preceded by a positive commandment is subject to flogging i.e. a lo saseah s'kedmu asseah]... He responded to them, No. [I retract what I said.] Rabbah said, By God! He said it. And it is backed by a posuk [verse] and a mishnah. It is written (Numbers 5,2) "And they shall send forth from the camp. etc. And they shall not defile their camps" [which is a lo saseah s'kedmu asseah] and it was taught in a mishna "One who enters the temple whilst impure [receives lashes].