21 Then Joab ordered a Cushite, "You go. Tell the king what you've seen." "Yes sir," said the Cushite, and ran off. 22 Ahimaaz son of Zadok kept at it, begging Joab, "What does it matter? Let me run too, following the Cushite." Joab said, "Why all this 'Run, run'? You'll get no thanks for it, I can tell you." 23 "I don't care; let me run." "Okay," said Joab, "run." So Ahimaaz ran, taking the lower valley road, and passed the Cushite. 24 David was sitting between the two gates. The sentry had gone up to the top of the gate on the wall and looked around. He saw a solitary runner. 25 The sentry called down and told the king. The king said, "If he's alone, it must be good news!"
Matthew Henry's Commentary on 2 Samuel 18:21-25
Commentary on 2 Samuel 18:19-33
(Read 2 Samuel 18:19-33)
By directing David to give God thanks for his victory, Ahimaaz prepared him for the news of his son's death. The more our hearts are fixed and enlarged, in thanksgiving to God for our mercies, the better disposed we shall be to bear with patience the afflictions mixed with them. Some think David's wish arose from concern about Absalom's everlasting state; but he rather seems to have spoken without due thought. He is to be blamed for showing so great fondness for a graceless son. Also for quarrelling with Divine justice. And for opposing the justice of the nation, which, as king, he had to administer, and which ought to be preferred before natural affection. The best men are not always in a good frame; we are apt to over-grieve for what we over-loved. But while we learn from this example to watch and pray against sinful indulgence, or neglect of our children, may we not, in David, perceive a shadow of the Saviour's love, who wept over, prayed for, and even suffered death for mankind, though vile rebels and enemies.