31 And he brought out the people that were in it, and put them under the saw, and under harrows of iron, and under axes of iron, and made them pass through the brickkilns. And so did he to all the cities of the children of Ammon. And 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.