LOL, finding out about Matthew 21:1-7 was probably the first time I realised the Bible was seriously flawed. Not only was Matthew not an eye-witness to this event; he seriously screwed up the translation from Hebrew to Greek, and it is now believed that he wasn’t a Jew, but someone living in Antioch in Syria.
A partial quote from ‘What are they saying about Matthew?’ (Paulist Press 1996):
Meier sees another Matthean "error" in the evangelist's excessively literal reading of Zechariah 9:9 in the account of Jesus' triumphant entry into Jerusalem. In Matthew's rendition of the scene (again in contrast to the parallel in Mark 11:1-10), the disciples are instructed to prepare "an ass ...and a colt" and Jesus sits on both (cf. Mt 21:7)! Commentators have traditionally explained this as Matthew's attempt to see a literal fulfillment of Zechariah 9:1) in this event of Jesus' life. Meier, however, thinks this also shows that Matthew misunderstands the Hebrew parallelism of 'Zechariah 9:9 where the reference to a donkey and a colt is not to two animals, but to one. Meier contends that only someone unfamiliar with Hebrew poetic forms, and, therefore, not a Jew, would be this literal on such an insignificant detail. Therefore, Matthew was not a Jew who became a ('Christian but a Gentile Christian who became well versed in the Hebrew scriptures and things Jewish.