God's glory filled the tabernacle and Temple; Moses asked to see God's glory, yet the fullness of God remained beyond ordinary human sight.
Exodus 25:8; Exodus 33:18-23; Exodus 40:34-38 provide the major presence-and-glory background.
John does not present Jesus merely as a messenger carrying information about God. The divine Word personally becomes flesh and makes the unseen God known.
The incarnation joins genuine humanity with the divine identity established in 1:1-3 and makes Jesus the embodied revelation of God's presence.