Every person must make himself a servant of G-d and must sanctify himself so as to come as close to the sanctity of the High Priest as is possible. He should practice some solitude and avoid emerging from this communion with G-d to the extent his circumstances allow. He must be concerned that no blemish, physical or spiritual, should attach to him. His striving must be that he himself should qualify as an offering to G-d. Once he endeavors to do all this is he considered "Holy to G-d".
The thrust of the legislation is that the court proclaims the dates when the various festivals are to be observed. (Lev. 23:2) We determine when to rejoice, when to eat festive meals. These festive meals should serve a spiritual purpose, just as did the delicacies Isaac ordered before blessing his son. When one approaches the holy days in this spirit, the second half of the verse, "These are My festivals", will be true. On the festivals, a person must not be so preoccupied with chores that he...loses...awareness of his special closeness to G-d...
If, however, these days are observed only as days when you fill your stomachs, indulge your body, then they are not "My festivals", but are vomit and excrement, concerning which the prophet has quoted G-d as saying: "My soul hates your festivals." (Isaiah 1:14) On the festivals, a person must not be so preoccupied with chores that he thereby should lose the awareness of his special closeness to G-d on such days.
The Zohar (Sulam edition, page 24) poses the question that if the legislation of not slaughtering the young animal on the same day as the mother animal (Lev. 22:28) is to save the mother animal the pain of watching its young killed, this could be avoided simply by keeping them apart. The true reason, however, is connected to the Jewish people's sense of empathy. To the extent that a person displays consideration for the feeling of others he in turn may find that such considerations of his own feelings will be a factor when he will be judged. The reverse is also true.[Translated and adapted by Eliyahu Munk.]