26 Now Joab fought against Rabbah of the people of Ammon, and took the royal city. 27 And Joab sent messengers to David, and said, "I have fought against Rabbah, and I have taken the city's water supply. 28 Now therefore, gather the rest of the people together and encamp against the city and take it, lest I take the city and it be called after my name." 29 So David gathered all the people together and went to Rabbah, fought against it, and took it. 30 Then he took their king's crown from his head. Its weight was a talent of gold, with precious stones. And it was set on David's head. Also he brought out the spoil of the city in great abundance. 31 And he brought out the people who were in it, and put them to work with saws and iron picks and iron axes, and made them cross over to the brick works. So he did to all the cities of the people of Ammon. Then David and all the people returned to Jerusalem.
Matthew Henry's Commentary on 2 Samuel 12:26-31
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.