As the mountains surround Jerusalem,
so the Lord surrounds his people,
from this time forth and forevermore. Psalm 125:2
It is not enough that we are compassed about with fiery walls, that is, with the sure custody, the continual watch and ward of the angels; but the Lord himself is our wall: so that every way we are defended by the Lord against all dangers. Above us is his heaven, on both sides he is as a wall, under us he is as a strong rock whereupon we stand so are we everywhere sure and safe. Now if Satan through these munitions casts his darts at us, it must needs be that the Lord himself shall be hurt before we take harm. Great is our incredulity if we hear all these things in vain.
—Martin Luther, as quoted in Spurgeon’s “Treasury of David”