(18) And it came to pass on the seventh day, that the child died. And the servants of David feared to tell him that the child was dead: for they said, Behold, while the child was yet alive, we spake unto him, and he would not hearken unto our voice: how will he then vex himself, if we tell him that the child is dead?
The seventh day prevented the act of circumcision. No doubt David construed this also as a further token of God's displeasure.