31 And he brought out the people who were in it and set them to labor with saws and iron picks and iron axes and made them toil at the brick kilns. And thus he did to all the cities of the Ammonites. Then David and all the people returned to Jerusalem.
Matthew Henry's Commentary on 2 Samuel 12:31
Commentary on 2 Samuel 12:26-31
(Read 2 Samuel 12:26-31)
To be thus severe in putting the children of Ammon to slavery was a sign that David's heart was not yet made soft by repentance, at the time when this took place. We shall be most compassionate, kind, and forgiving to others, when we most feel our need of the Lord's forgiving love, and taste the sweetness of it in our own souls.