Summary of 7th Aliya
The Levites, too, will not receive a share of the land of Israel. Instead they are entitled to a tenth of all the Israelites' crops—this in return for the Tabernacle and Temple services which they render. Upon receiving this tithe, the Levites must, in turn, separate a tenth of this tithe and give it to the priests.
(28) so shall you on your part set aside a gift for the LORD from all the tithes that you receive from the Israelites; and from them you shall bring the gift for the LORD to Aaron the priest.
אמר קרא אתם (במדבר יח, ג) גם אתם לרבות את השליח
The verse states with regard to teruma: “So you also shall set apart a gift unto the Lord of all your tithes” (Numbers 18:28). Once the verse states “you,” the addition of the word “also” in the term “you also” serves to include an agent.
עוד
Marriage (Kidushin)/Divorce
Shliach Tzibur (Chazzan)
Korbonos (the Kohanim)
Separating Challah,
(א) מִצְוַת עֲשֵׂה עַל הָאָב לָמוּל אֶת בְּנוֹ, אוֹ לְכַבֵּד וְלַעֲשׂוֹת שְּׁלִיחַ לְיִשְֹרָאֵל אַחֵר שֶׁיָמוּל אוֹתוֹ. וּ הָרִאשׁוֹן.
(1) It is a positive mitzvah for the father to circumcise his son, or to grant the honor and appoint another Jew as his agent to circumcise him.
מצוות שבגופו
אין שליח לדבר עבירה
Exceptions:
(ד) אפילו מי שיש לו כמה עבדים יש לו להשתדל להכין בעצמו צרכי שבת שכן הוא בכל המצות מצוה בו יותר מבשלוחו. ואפילו מי שהוא אדם חשוב ביותר ואין דרכו ליקח דברים מן השוק ולא להתעסק במלאכות שבבית חייב להשתדל ולעשות שום דבר מצרכי השבת בעצמו שזהו כבודו של שבת וגדולי החכמים היו עושים בעצמם מלאכות שאינן לפי כבודם כדי להרבות בכבוד השבת יש מהם שהיה מחתך הירק דק דק בעצמו ויש מהם שהיו מבקעים עצים בעצמם ויש מהם שהיה מצית האור תחת העצים בעצמו ויש מהם שהיה מתקן הבית ומפנה כלי החול ומכניס כלים הצריכים לשבת ובעסק זה היה יוצא ונכנס תמיד בביתו בערב שבת להוציא כלי החול ולהכניס משאות כלי תשמיש ובגדי חופש ומיני מגדים להראות כבוד השבת שהוא חשוב עליו וחרד לכבודו כאדם שמקבל את רבו בביתו שהוא מראה לו שהוא חשוב עליו וחרד לכבודו לטרוח ולהרבות בשבילו ומהם ילמוד כל אדם לטרוח בעצמו ואל יאמר איך אפגום כבודי כי זהו כבודו שמכבד השבת:
עוד
Clean Shul
Bris
Kidushin etc. (all Mitzvos)
למה?
Why?
Reason behind Shluchim.
...מכאן ששלוחו של אדם כמותו
... Rather, it can be derived from here that the legal status of a person’s agent is like that of himself.
שלוחי ה'
We are all Shluchim of Hashem to do Torah & Mitzvos
Summary:
We learn out the law of being an agent for another person, to do a Mitzvah for him, from the wording the Torah uses to command the Levites to gift Terumah from their gifts, "Also you", From here we learn the general law of Shlichus and that a non Jew cannot be an agent.
The reason for this is since the agent represents the sender. Not only does he represent him but he is "wearing his shoes", he has now become the sender himself, all that he does is credited to the sender and it is as if the sender himself is performing the act.
For this reason (the messenger has the full power and becomes the sender to fulfill this task), the messenger has to be somewhat similar and have a common denominator with his sender, there needs to be some common ground. Thereby a non Jew, who cannot equate with a Jew in the realm of Torah and Mitzvos can not be his Shliach. (This same reasoning would apply to a Cheiresh, Shoteh and a Koton).
The same to applies for everyone, each Jew is an ambassador of the Almighty sent down to this world to fill it with the light of Torah and Mitzvos. One may ask, with what can I be compared to Hashem, to be able to be his messenger? The answer is that we all posses a part of Hashem inside of us, because of this we can be somewhat 'similar' to Hashem and be considered his messenger.
In the realm of Halakha this concept is very important, as laid out in the sources above.
(Interesting to note that in the Parsha of Korach, this is a dispute as to Why is Moshe (and Aharon) considered the ambassadors of Hashem.
Also we read about the encounter Aharon has, as a Shliach of Moshe, with the Angel of Death.
In History: Moshe is appointed the Shliach of Hashem "Shlach Na, Byad Tishlach" to redeem to Jewish People from Egypt, and Moshe (his representative - Moshiach) with redeem us from this current Golus and bring us to the Geulah).