Holy Zohar text. Daily Zohar -54.

The letters of the word Shabbat שבת, reveal the process of Shabbat. The letter ש, built from three Vav ו, reveal the connection to the supernal three with the help of the three patriarchs, that are Chessed, Gevurah and Tiferet of Zeir Anpin.
בת means daughter, as the daughter of supernal Father, Chokmah and Mother, Binah.
ב is for the house, בית, which was built for us below and filled with light in Shabbat.
ת is the final letter for Malchut, where everything is manifested.

מקור הקטע: הקדמת תיקוני הזוהר עם פרוש מעלות הסולם (רבי יהודה צבי ברנדויין זל) פסקה 258