The phrase "the gate of heaven" explains that this place is the entrance to "the house of God" and "the entrance to where God lives." (See: [[rc://en/ta/man/jit/figs-doublet]])
This speaks about the entrance to the place where God lives as if it were a literal kingdom that had a gate that someone has to open to let people in. (See: [[rc://en/ta/man/jit/figs-metaphor]])