Rashi on Leviticus 23:35/רש"י על ויקרא כ״ג:ל״ה

1מקרא קדש — This means: Hallow it (make it different from other days) by wearing fine clothes, and through appropriate prayer. In the case of other Festivals of which the same words are used, the expression מקרא קדש implies: Hallow them (distinguish them from other days) by your food and drink, by your fine clothes and appropriate prayers (cf. Sifra, Emor, Section 12 4).