Zohar Shemot 88A
Rabbi Shimon said: When a man has completed the three meals on Shabbat, a voice comes forth and proclaims of him: "Then shall you delight yourself in G‑d" (Isaiah 58:14). This is in reference to one [the first] meal (on Friday night), which corresponds to Atika Kadisha, the holiest of all the holy levels. "And I will cause you to ride upon the high places of the earth" refers to the second meal, which corresponds to "Chakal Tapuchin Kadishin/Holy Apple Field" [malchut]. "And feed you with the heritage of Jacob your father" is the perfection it reaches [as Atika Kadisha flows through] into Zeir Anpin [at the third meal after Mincha].
Corresponding to this, one should complete the meals and find joy in each and all of them because this is a manifestation of perfected faith. Therefore, Shabbat is more precious than all other times and holidays because it contains all in itself, whereas no other times or holidays do so. Rabbi Hiya said: Because all [the partzufim of Atzilut] are present in Shabbat, it is mentioned three times: "And by the seventh day G‑d [the level of malchut] finished His work which He had done... And He [Atik – hidden and not specifically mentioned by name] rested on the seventh day from all His work which He had done... And G‑d [the level of Zeir Anpin] blessed the seventh day and sanctified it". (Gen. 2:2-3)
When Rav Hamnuna Saba sat at his Shabbat meals, he used to rejoice in each one of them and he would say: This is the holy meal of Atika Kadisha, the most hidden of all. [Then he would specify at each meal the particular level that Atika Kadishawas uniting with.] Over another he would add: This is the meal of the Holy One, blessed be He, and so in each and every meal. [over Friday night meal he would add this is the meal of the "Holy Apple Field" and in the morning “this is the meal of Atika Kadisha”] And when he came to the last one, he would say: The meals of faith are completed.
When Rabbi Shimon sat at his meals, he would say: We have prepared the meal of the supernal faith [in Atzilut]! We have prepared the meal of the King! And then he would sit and rejoice. When the third meal was completed, he would announce: "Then shall you delight yourself in G‑d and I will cause you to ride upon the high places of the earth and feed you with the heritage of Jacob your father."