Leviticus 23:2

Speak unto the children of Israel, and say unto them
Speak to them to gather together, and then say unto them what follows, they all being obliged to keep the feasts, and observe the solemnities hereafter directed to; though it may be the heads of the tribes and the elders of the people were summoned together, and the following things were delivered to them, and by them to the people: [concerning] the feasts of the Lord, which ye shall proclaim [to be]
holy convocations, [even] these [are] my feasts;
appointed and ordered by God, and to be kept to the honour of his name; these are the general names for the particular holy times and seasons after appointed; they are in general called "feasts", though one of them, the day of atonement, was, strictly speaking, a fast; yet being a cessation from all work, and opposed to working days, days of labour and business, it is comprehended in this general title: nor is it unusual with other nations to call a fast a feast; so Aelianus ^F8 relates of the Tarentines, that having been besieged by the Romans, and delivered from them, in memory of their sufferings appointed a feast which was called a fast: the word used has the signification of stated, fixed, appointed times and seasons, and of convening or meeting together at such times, and that for the performance of solemn worship and service, which is true of them all; for there are certain times of the week and month fixed for them, and when the people in bodies assembled together, and in a solemn manner worshipped the Lord; and these are called "convocations", because the people were called together at those times by the priests, and that with the sound of a trumpet, ( Numbers 10:2 Numbers 10:3 Numbers 10:8-10 ) ; and "holy", because separated from other days, and set apart for holy services: the words may be rendered, as they are by many ^F9: "the solemnities of the Lord, which ye shall proclaim holy convocations, these are my solemnities"; times for holy, religious, and solemn service, of his appointment and for his glory: Aben Ezra seems to understand all this of the sabbath only, which is next mentioned, expressed in the plural number, because, as he observes, there are many sabbaths in a year; and indeed the general title of the rest of the feasts is afterwards given, ( Leviticus 23:4 ) .