Why were there no windows in the tabernacle?
Within the whole complex, no windows were included because God Himself, or Christ as the light of the world, was to be the sole light. The sanctuary's illumination thus pointed to divine presence rather than natural light from outside; no created source supplied it.
Les explains that there were no windows within the whole tabernacle complex because the question is, “Who alone can be the light?” The answer is God Himself, or Christ again, as the light of the world. So as one came into the sanctuary, the absence of windows kept the focus on the divine light rather than natural light. This fits the broader construction: the wood frame was acacia wood, speaking of Christ’s humanity, covered with gold, speaking of His deity, except the brazen altar, which was covered with brass. Inside was hand-woven linen with blue, purple, red, and white, and cherubim-like angelic beings woven into the fabric.