In Isaiah 26:9, this signifies people of the church in the goods of doctrine and life. (Apocalypse Explained 741[6])

Down" is used many different ways, and its spiritual meaning in the Bible is highly dependent on context. Phrases like "bowing down," "lying down" and "falling down" are defined primarily by "bowing," "lying" and "falling"; there is also a great difference between a person descending, the Lord sending fire from heaven and someone handling an object, to offer a few examples. In a very general sense, though, "down" indicates a lowering from more internal spiritual states to more external ones. That's why the journey is described as going "down" to Egypt from Canaan, and people from all quarters go "up" to Jerusalem. It's also why the Lord comes "down" to us, which generally indicates a state of judgment.