Based on Matthew 21:1-11 (and similar passages in Mark 11, Luke 19, and John 12), the text was originally written for a Palm Sunday procession. Thus it reflects on the original Palm Sunday's hymns of praise by the Jews as well as on our praise today.
In Stanza 1, Christ is referred to as the “King of Israel and David’s royal Son” and “the King and blessed one.” Belgic Confession, Article 18 traces Christ’s lineage to David as well: Christ is “descended from David according to the flesh...”