The entire week, a person is preoccupied with the daily concerns of making a living and all the other preoccupations of the week. Nevertheless, one must set aside time to study the Torah every day. But if one was unable to study during the week then, at the very least, on Shabbath one must make the effort to study Torah and not spend the entire day simply eating, drinking and sleeping. Our Rabbis of blessed memory tell us that Shabbath and Yom Tob (Holy days) were only given to us in order to study Torah and one who does not waste time has time for everything.
The importance of learning Hiddushei Torah (new Torah insights) on Shabbath is great. It says in the holy Zohar that on Mosei Shabbath (when Shabbath finishes) the Neshamah Yethera (additional soul that we receive on Shabbath) returns to Heaven. The Holy One Blessed Be He asks it: "What Hiddush Torah (new Torah insights) did you learn today?" After which the soul is seated in the Yeshibah on high.
(see 'Abodath Haqqodesh - Morei Be'esba' 153. Kaf Hahayyim 300, Oh 13.)
