Lift up your heads, O ye gates; and be ye lift up, ye everlasting doors; and the King of Glory shall come in! Who is this King of Glory? The Lord strong and mighty, the Lord mighty in battle. Lift up your heads, O ye gates; even lift them up, ye everlasting doors; and the King of Glory shall come in! Who is this King of Glory? The Lord of Hosts, He is the King of Glory. (Psalms 24:7-10)

Through what gates is the King of Glory proceeding? In the original psalm it was probably Jerusalem and the temple precinct. Given the oratorio's narrative, Handel and Jennens might have been thinking of the gates of heaven.

It could also be the gates to my mind and heart. I erect walls, redoubts, gates, and towers to protect and separate. The defences were originally constructed to exclude threat and hurt. But without care they will equally separate me from what is good.

A great and glorious host is gathered outside my walls. Bright banners stream in the wind, loud trumpets sound, and drumming rhythm vibrates through me. The King of Glory has arrived. Will I choose to open my gates?

You can listen to Lift up your Heads from the Messiah performed by the Academy of St. Martin's in the Fields.