"Yeah in this wasteland where I'm livin'
There is a crack in the door filled with light
And it's all that I need to get by"
In more than one way, this world is like a wasteland. It's overrun by sin and temptation and darkness.
The "crack in the door filled with light" is the Gospel. throughout His ministry, Jesus likens the Gospel to a light in the darkness (Psalm 119:105; John 1:5-9; John 8:12; John 12:35-37). A dark room is overcome by the light rushing in from a cracked door. The Gospel is that light.
-"it's all that I need to get by" is simply stating that having the Gospel is all that he needs to get by in this life (Isaiah 40:31; Romans 15:13; Romans 8:24-25).
Lastly,
"Oh if God is on my side
Yeah if God is on my side
Oh if God is on my side
Who can be against me"
If we have the Gospel (God on our side), then what can overcome us?(Romans 8:31)
I love the metaphor in the chorus!
"Yeah in this wasteland where I'm livin' There is a crack in the door filled with light And it's all that I need to get by"
Lastly, "Oh if God is on my side Yeah if God is on my side Oh if God is on my side Who can be against me"