Adam Clarke on Exodus 12:16

In the first day and in the seventh day there shall be a holy convocation - This is the first place where we meet with the account of an assembly collected for the mere purpose of religious worship. Such assemblies are called holy convocations, which is a very appropriate appellation for a religious assembly; they were called together by the express command of God, and were to be employed in a work of holiness. מקרא mikra, convocation, is a word of similar import with the Greek εκκλησια, which we commonly translate Church, and which properly signifies an assembly convened by public call.