Like arrows in the hand of a warriorOk. Imagine a warrior (an archer, more specifically). Imagine this archer all geared up and ready for battle. Now, imaging that this archer has no arrows. He has the quiver. He has the bow. Everything else is ready to go, but no arrows.
are the children of one's youth.
Now, imagine that same archer, except that there are arrows in his hand. How does that change the picture?
Children do change the picture, and according to the psalmist, in a similar way that arrows change the picture. Sure, you can still be a warrior without the arrows, but with the arrows (and a bow) you have added potential in a battle. You are no longer just a foot soldier. You can begin fighting long before the enemy makes its way to you.
Children do a similar thing. They are part of a well-formed family and add to the families potential.