Likutei Moharan, Part II 17:2/ליקוטי מוהר"ן·תנינא י״ז:ב׳

12. This is the rule: A person has to behave very joyously on the holy Shabbat, never displaying even a hint of depression or anxiety. Rather, he should delight in God and treat himself to all kinds of Shabbat delights—food, drink, clothing… whatever he can afford. Shabbat eating is purely spiritual. It is entirely holy and rises to a place which is totally different from that of weekday eating, as explained elsewhere. (See Likutey Moharan I, 57:5 and 277:4; see also Zohar II, 218a and Mikdash Melekh there.).