Lift up your heads, O ye gates; and be ye lift up, ye everlasting doors; and the King of glory shall come in. Lift up your heads, O ye gates - The address of those who preceded the ark, the gates being addressed instead of the keepers of the gates. Allusion is here made to the triumphal entry of a victorious general into the imperial city.
In the hymn of Callimachus to Apollo, there are two lines very much like those in the text; they convey the very same sentiments. The poet represents the god coming into his temple, and calls upon the priests to open the doors, etc.
Αυτοι νυν κατοχηες ανακλινεσθε πυλαως,
Αυται δε κληιδες· ὁ γαρ Θεος ουκ ετι μακραν;
"Fall back, ye bolts; ye pond'rous doors, give way
For not far distant is the god of day."
Callim. Hymn in Apol., ver. 6, 7.
The whole of this hymn contains excellent sentiments even on the subject of the Psalms.
Everlasting doors - There seems to be a reference here to something like our portcullis, which hangs by pullies above the gate, and can be let down at any time so as to prevent the gate from being forced. In the case to which the psalmist refers, the portcullis is let down, and the persons preceding the ark order it to be raised. When it is lifted up, and appears above the head or top of the gate, then the folding doors are addressed: "Be ye lift up, ye everlasting doors;" let there be no obstruction; and the mighty Conqueror, the King of glory, whose presence is with the ark, and in which the symbol of his glory appears, shall enter. Make due preparations to admit so august and glorious a Personage.