(Devarim 18:6) "And if the Levite come": I might think that Scripture speaks of a Levite per se; it is, therefore, written (7) "And he shall serve" — (Scripture speaks of) those who are qualified to serve (i.e., the Cohanim, who perform the sacrificial service), to exclude the Levites, who are not thus qualified.
Whence is it derived that a Cohein may come and offer his (own) sacrifices whenever he wishes (though his watch not be officiating at that time)? From "then he shall come in all the desire of his soul … (7) and he shall serve." Whence is it derived that a Cohein may come and lift his hands (in the priestly blessing) in a watch that is not his? From "then he shall come in all the desire of his soul … and he shall serve in the name of the L-rd his G-d." Which is service in the name of the L-rd? The priestly blessing.
Whence is it derived that all the priestly watches share equally in the (devoted portions of the) offerings of the festival? From (6) "then he shall come in all the desire of his soul to the place that the L-rd shall choose." I might think that the same holds true for all the days of the year; it is, therefore, written (6) "from one of your gates" — when all of Israel are assembled within one gate, i.e., during the three festivals.
(דברים יח ו) וְכִי יָבֹא הַלֵּוִי, יָכוֹל בְּבֶן לֵוִי וַדַּי הַכָּתוּב מְדַבֵּר? תַּלְמוּד לוֹמַר: מֵאַחַד שְׁעָרֶיךָ, מִי שֶׁלֹּא נָטְלוּ שְׁעָרֵיהֶם בְּמָקוֹם אַחֵר; יָצְאוּ לְוִיִּם, שֶׁנָּטְלוּ שְׁעָרֵיהֶם בְּמָקוֹם אַחֵר. (דברים יח ז) ״וְשֵׁרֵת״ – בָּרָאוּי לְשָׁרֵת; יָצְאוּ לְוִיִּם, שֶׁאֵין רְאוּיִים לְשָׁרֵת.
(Devarim 18:6) "And if the Levite come": I might think that Scripture speaks of a Levite per se; it is, therefore, written (7) "And he shall serve" — (Scripture speaks of) those who are qualified to serve (i.e., the Cohanim, who perform the sacrificial service), to exclude the Levites, who are not thus qualified.
(דברים יח ו) מִכָּל יִשְׂרָאֵל אֲשֶׁר הוּא גָּר שָׁם – בְּכָל מְקוֹמוֹת מוֹשְׁבוֹתֵיהֶם.
"from all of Israel wherein he lives": in all of the places of their dwellings":
וּבָא בְּכָל אַוַּת נַפְשׁוֹ, מִנַּיִן אַתָּה אוֹמֵר, כֹּהֵן בָּא וְנוֹשֵׂא אֶת כַּפָּיו בְּמִשְׁמָר שֶׁאֵינוֹ שֶׁלּוֹ? תַּלְמוּד לוֹמַר: וּבָא בְּכָל אַוַּת נַפְשׁוֹ,
Whence is it derived that a Cohein may come and offer his (own) sacrifices whenever he wishes (though his watch not be officiating at that time)? From "then he shall come in all the desire of his soul … (7) and he shall serve." Whence is it derived that a Cohein may come and lift his hands (in the priestly blessing) in a watch that is not his? From "then he shall come in all the desire of his soul … and he shall serve in the name of the L-rd his G-d." Which is service in the name of the L-rd? The priestly blessing.
מִנַּיִן אַתָּה אוֹמֵר כָּל הַמִּשְׁמָרוֹת שָׁוִים בְּקָרְבְּנוֹת הָרֶגֶל הַבָּאִים מֵחֲמַת הָרֶגֶל? תַּלְמוּד לוֹמַר: וּבָא בְּכָל אַוַּת נַפְשׁוֹ. יָכוֹל לְעוֹלָם? תַּלְמוּד לוֹמַר: מֵאַחַד שְׁעָרֶיךָ, בְּשָׁעָה שֶׁיִּשְׂרָאֵל מְכֻנָּסִים בְּשַׁעַר אֶחָד, בְּשָׁלֹשׁ רְגָלִים.
Whence is it derived that all the priestly watches share equally in the (devoted portions of the) offerings of the festival? From (6) "then he shall come in all the desire of his soul to the place that the L-rd shall choose." I might think that the same holds true for all the days of the year; it is, therefore, written (6) "from one of your gates" — when all of Israel are assembled within one gate, i.e., during the three festivals.