And we will cite the prophetic utterances of another prophet, Zephaniah, to the effect that He was foretold expressly as to sit upon the foal of an ass and to enter Jerusalem. The words are these: "Rejoice greatly, O daughter of Zion; shout, O daughter of Jerusalem: behold, thy King cometh unto thee; lowly, and riding upon an ass, and upon a colt the foal of an ass."
Source: The First Apology, Chapter XXXV