Musar על שבת 235:8

This answer seems difficult since we still do not know exactly what is the nature of the reward for Sabbath observance. One can answer this difficulty only by referring to the many statements of our sages equating Sabbath observance with total מצות observance. This is so in spite of the fact that the observance of the Sabbath legislation involves many more pleasant aspects as opposed to the efforts and sometimes deprivations involved in the performance of other commandments. I have enlarged on this subject in my commentary on Song of Songs 7,7: "How beautiful and pleasant are you, befitting the pleasures of love in delights." This aspect of the reward for Sabbath observance has thus been revealed to us.