Work on Shabbat
Serving Hashem during the six days of the week is accomplished through "you shall do all your work"—by ensuring that all your actions are for the sake of Heaven.
On Shabbat, however, the Torah says, "you shall not do any work." Serving Hashem on Shabbat is accomplished through refraining from work.
(Rabbeinu Bachye)
Sanctifying Shabbat
Shabbat is inherently holy, for Hashem blessed the seventh day and sanctified it. Nevertheless, the Torah commands, "remember the Shabbat day to sanctify it", instructing us to sanctify Shabbat.
For when the Jewish people remember Shabbat, they add an additional dimension of holiness to its inherent sanctity.
(Sefat Emet)
Desires Granted
Whoever delights in Shabbat is granted the desires of his heart, as it says, "so shall you delight in the L-rd, and He will give you what your heart desires." (Tehillim 37:4).
(Shabbat 118a)
Shabbat Delight
The pleasure experienced in Shabbat prayer is spiritual pleasure. The pleasure of the Shabbat meal is both spiritual and physical. Yet ultimately, it is all G-dly pleasure, for on Shabbat even our natural faculties are elevated through the Divine light revealed on that day.
(the Rebbe Rashab)