When you read the first reading today, it seems unfair. After the repentance of the king God says, "I will not bring the evil in his time. I will bring the evil upon his house during the reign of his son."
On the surface it seems to be unfair. Why would God punish a child for the actions of his son. The short answer is, he wouldn't. While the Old Testament tends to state everything in a simple language that reads to us like direct divine intervention, what is really being described here is consequences.
Our actions are never single acts in perfect isolation. Because we live in relationship to others all of our actions have ripple effects. Some we see; some we don't see. Some we intend, some not.
When a pregnant woman does drugs, is it God punishing the child when it is born with problems? In our modern language we would recognize that it is the consequence of her action, not divine punishment.
Today's reading reminds us of a stark, painful truth. There are times when we can feel true contrition, and be truly forgiven by God, but as the expression goes, you can't unring the bell. There are times when we have to live with the effects of the choices we made.
Today's first reading is a reminder of why it is so important that we think before we act. Can we foresee every effect? No. But it is a safe bet that when we chose sin, there is going to be a negative ripple.
Once more we come back to fundamental moral theology. What distinguishes a human act is intellect and will, the ability to think and chose.