Commentary of Charles Spurgeon, Adam Clarke & Matthew Henry
Now the Philistines gathered together their armies to battle, and were gathered together at Shochoh, which belongeth to Judah, 
and pitched between Shochoh and Azekah, in Ephesdammim. And Saul and the men of Israel were gathered together,
and pitched by
the valley of Elah,
and set the battle in array against the Philistines.
And the Philistines stood on a mountain on the one side,
and Israel stood on a mountain on the other side:
and there was a valley between them.
Vs.1-3
So we shall proceed at once to regard David, in his conflict with Goliath, and his victory over him, first, as a type of our Lord Jesus Christ, and, secondly, as an example for ourselves. 
As that which is a type of the head always bears a relationship to the
members, and as the members of Christ's mystical body now are, and shall
yet more fully be, like unto Himself.
The Philistines (it is probable) had heard that Samuel had fallen out
with Saul and forsaken him, and no longer assisted and advised him, and
that Saul had grown melancholy and unfit for business,....
---The enemies of the church are watchful to take all
advantages, and they never have greater advantages than when her
protectors have provoked God's Spirit and prophets to leave them.
Shochoh and Azekah — Places which lay to the south of Jerusalem and to the west of Bethlehem.
The valley of Elah — Some translate this the turpentine valley, or the valley of the terebinth trees; and others, the valley of oaks.
Israel's ground would never have been footing for Philistine-armies if Israel had been faithful to their God.
