The 149th prohibition is that kohanim are forbidden from eating bikkurim outside [Jerusalem].
The source of this prohibition is G‑d's statement,1 "In your own settlements, you may not eat...the terumah of your hand." The Oral Tradition2 explains that [the phrase] " 'the terumah of your hand' refers to bikkurim," since the verse explicitly mentions everything else which must be brought [to Jerusalem]. The general phrase, "the terumah of your hand" undoubtedly refers to bikkurim, which the Torah clearly says3 must be brought [to Jerusalem]. [We know that this phrase could not refer to regular terumah because] it is well known that regular terumah need not be brought [to Jerusalem]; so how could there be a prohibition to eat it "in your own settlements"? [This point is said clearly] in the words of the Sifri: "This phrase speaks only of bikkurim, which the verse does not mention explicitly as being prohibited."
It is explained in the end of Makos4 that the prohibition applies only [if he eats them] before they are placed in the Temple courtyard. But once they have been placed in the courtyard — even if the proclamation5 has not yet been made — one is exempt from punishment.
The same condition which applies to ma'aser sheni governs bikkurim, i.e. the prohibition applies only after they have "seen the face of the Temple" [i.e. were brought inside the walls of Jerusalem]. The prohibition is transgressed if they are eaten after they have entered Jerusalem and before they have been placed in the courtyard. If he is a kohen, he is punished by lashes; if an Israelite, his punishment for eating bikurim is a heavenly death sentence [misah biy'dei shamayim], even if the proclamation was made. Our Sages explicitly said,6 "For terumah and bikkurim one must add a fifth; their punishment is death; and they are prohibited to non-kohanim." [This means that] if he ate them intentionally, he is punished with misah biy'dei shamayim; if it was unintentional, he must [pay the value and] add on an additional fifth, as is the case with terumah. The reason for this is since the verse calls it "the terumah of your hand," all the laws of terumah apply.
You should understand this well in order to avoid confusion: a kohen who eats bikurim after they have entered Jerusalem and before they have been placed in the courtyard is punished by lashes. The source of this prohibition is the verse, "In your own settlements, you may not eat...the terumah of your hand," as explained in Makos. This is just like the law of an Israelite who eats ma'aser sheni outside the proper place — he is punished by lashes even though the food belongs to him.
But an Israelite who eats bikurim after they were brought to Jerusalem is punished by misah biy'dei shamayim regardless of where he ate them. The source of this prohibition is the verse,7 "Any non-kohen may not eat sanctified objects," as explained in Prohibition 133.
The details of this mitzvah are explained in tractate Makos.
