Why does David mourn the death of his adult son Absalom and not the death of his baby son?

Question

When David's son from Bathsheba died David stopped mourning and got up and ate, stating that nothing could be done for his son now:

[21] Then his servants said to him, “What is this thing that you have done? You fasted and wept for the child while he was alive; but when the child died, you arose and ate food.” [22] He said, “While the child was still alive, I fasted and wept, for I said, ‘Who knows whether the LORD will be gracious to me, that the child may live?’ [23] But now he is dead. Why should I fast? Can I bring him back again? I shall go to him, but he will not return to me.” (2 Samuel 12:21-23 ESV)

Latter in the same book when David hears that his sons (who was trying to take his throne) is dead he grieved:

[33]  And the king was deeply moved and went up to the chamber over the gate and wept. And as he went, he said, “O my son Absalom, my son, my son Absalom! Would I had died instead of you, O Absalom, my son, my son!” (2 Samuel 18:33 ESV)

David was rebuked for mourning (2 Sam 19ff), but did David not grieve for his baby son as he knew the baby would be in heaven (2 Sam 12:23b) and that Absalom wouldn't be? If this is correct, can this reasoning be applied to all babies who die?

Answer 1

David accepted the death of his child by Bathsheba as punishment for his sin with her and he let that overcome his grief. (The status of the child’s soul is a question for elsewhere.) There was no such consideration in the case of Absalom, and David was overcome by father’s grief. Joab berates him for this, saying that his grief threatens morale.

(Off-topic, but I’ll mention it anyway: The Midrash notes that David called Absalom “my son” eight times between verses 1 & 5; seven to raise him from the seven levels of Gehinnom and the eighth to raise him into Heaven.)

Answer 2

According to the Me'am Lo'ez, some explain the behavior by reference to the following law: if a fast is decreed due to a lack of rainfall, then when it rains, the people should stop fasting. But, if an individual fasts for someone who is ill, and that person recovers, he still must complete that fast (through sundown). In the latter case, there is still a chance of relapse, so the fast must be completed. But where the patient dies, there is no reason to continue the fast, further fasting serves no purpose. David explains this in the next verse (2 Sam. 12:22-23). David did in fact grieve the lost of his young son, but mourners are allowed to eat. In contrast, Avsalom -- even if he tried to kill his father -- was still David's son and David's grief was very appropriate.

Answer 3

David's dead 7-day old baby was immediately taken into Paradise-- Abraham's bosom (see Luke 19)since the child was not at the age of accountability, not being able to discern right from wrong. God took this baby right into Paradise since the baby was unable to either accept or reject God. However, Absalom, his adult son, most likely rejected the God of his father David. When Absalom died as an unrepentant adult, he went not to paradise but rather into the flames of Hell forever.

David therefore knew that he lost Absalom forever, his baby for only a time. Absalom's fate in torment was a horrible grief of mind to King David, far greater than the grief of losing his baby son. David knew that his baby was in the comfort of Paradise, where David, a man after God's own heart, would go himself after death.