The 78th prohibition is that a person who is tameh is forbidden from entering the machaneh Leviyah, which later corresponded to the Temple Mount, as we explained in our commentary on the beginning of tractate Keilim.1 The prohibition against people who are tameh entering the Temple Mount is explained there.

The verse which serves as the source of this prohibition refers to a man who is tameh because of a nocturnal emission, "He may not enter inside the camp."2

The passage3 in tractate Pesachim4 reads: "The phrase 'he must go outside the camp' refers to the machaneh Shechinah," as we explained in positive commandment 31. [Pesachim continues,] "The phrase 'he must go outside the camp' refers to the machaneh Leviyah."

"Ravina then asked, 'perhaps both phrases refer to the machaneh Shechinah, and the repetition serves to cover both the positive and negative commandments?!'"

[The Gemara answers,] "If so, it could have just written, 'he may not enter inside,'" i.e., "he may not enter inside it."5 [The Gemara continues,] "Why is the word 'camp' repeated? To refer to a second type of camp, i.e., the machaneh Leviyah." This means that even this camp he may not enter.

The Sifri6 says [clearly that this phrase counts as a separate commandment]: "The phrase, 'He may not enter inside the camp, 'is a negative commandment."

The details of this mitzvah are also explained in our commentary to the beginning of tractate Keilim.