Sukkos - ברך משה 55 שישו ושמחו
"ישמח משה במתנת חלקו כי עבד נאמן קראת לו, כליל תפארת בראשו נתת לו בעמדו לפניך על הר סיני, ושני לוחות אבנים הוריד בידו וכתוב בהם שמירת שבת" - "Moshe rejoiced in the gift of his portion, for You called him a faithful servant. You placed a crown of splendor on his head for him, when he stood before You on Har Sinai. He brought down in his hands two tablets of stone and inscribed upon them was the observance of Shabbos." This is said in the Shemoneh Esrei of Shabbos morning, and some say it by the fourth Hakafah on Simchas Torah. What is the "מתנת חלקו" that we are referring to, and what is the connection to heeding Shabbos Kodesh?
The Gemara in Shabbos 88a says that at the time that Klal Yisroel said, "נעשה ונשמע", six hundred thousand Malachei Hashareis came to give crowns to each one of the six hundred thousand of Klal Yisroel. They tied the two crowns that each person received, one for saying נעשה and one for saying נשמע. When Klal Yisroel sinned with the Eigel, 1.2 million Malachim came down and removed the crowns from Klal Yisroel, as the Posuk in Shemos 33:6 says, "ויתנצלו בני ישראל את עדים מהר חורב". Rebbe Yochanon says that Moshe Rabbeinu was Zoche to all of these crowns which were taken from Klal Yisroel, as the Posuk says "ומשה יקח את הואהל" and Rashi says it is from a Loshon of "בהלו נרו" from Iyov 29:3 - "His lamp shone" - meaning that Moshe's face was illuminated. It says in Targum Yonason on this Posuk that Moshe Rabbeinu took that great light and hid it in the Torah Hakdosha. Anyone from Klal Yisroel who toils in the Torah Hakdosha with Kedusha and Taharah, they are Zoche to tap into that bright illuminating light which comes from those crowns. This is why we have seen by the great Tzaddikim that their faces shine like the sun, for through the Torah Hakdosha they are Zoche to this light which comes from those crowns of Matan Torah which was hidden in the Torah Hakdosha.
It says in the Ohr Hachaim Hakodosh in Parshas Vezos Habrocha in the name of R' Chaim Vital that on the holy day of Shabbos Kodesh Moshe Rabbeinu returns the crowns to Klal Yisroel, and Moshe Rabbeinu is left with his own crowns. This is what we say that Moshe was happy "במתנת חלקו" that Moshe Rabbeinu was happy with his own portion on Shabbos Kodesh, for every Shabbos he returns all the crowns of Klal Yisroel to them, thus, he remains with only his own portion. This is what Chazal mean when it says in Bereishis Rabbah 11:2 that you cannot compare the light of a Yid's face during the week to that of Shabbos, because on Shabbos Kodesh Klal Yisroel get back the crowns, the light of the crowns, and it illuminates their faces. This is what we say on Shabbos morning, and during the Hakafos, that Moshe is a faithful servant, one who returns the crowns to Klal Yisroel "כליל תפארת בראשו נתת לו בעמדו לפניך על הר סיני". The splendor of crowns which Klal Yisroel were Zoche to at Har Sinai, but lost then when they sinned, Moshe Rabbeinu returns it to them - in one of two ways: "ושני לוחות אבנים הוריד בידו" - He hid it in the Torah, so that if they toil in Torah they can access it, and "וכתוב בהם שמירת שבת" through the Kedusha of Shabbos Kodesh.