"On the seventh day the child died" (2 Sam. 12:18). Is there a way textually or contextually to know if these seven days refer to the age of the infant, or instead, seven days of sickness?
Before simply answering "seven days," let's look at the preceding verse:
15 So Nathan went to his house. Then the Lord struck the child that Uriah’s widow bore to David, so that he was very sick.
The specific time of the birth is not stated; nor is the moment when the Lord struck the child. The sequence is clear, but not the timing. Bathsheba marries David in the previous chapter. After this, Nathan makes his prophecy. The child is not yet born, since Nathan states: "because by this deed you have given occasion to the enemies of the Lord to blaspheme, the child also that is born to you shall surely die." (vs 14)
Nathan then goes back to his house while Bathsheba is still apparently pregnant. "Then" the Lord strikes the child, but exactly when (how long after it was born) is not said. What IS specified is the length of time between the onset of the illness and death: seven days. We naturally tend to assume the illness was birth-related but this is a presumption. The child could have been weeks or months old before being struck, perhaps even years.
Conclusion: although the most natural answer is seven days, this is not certain. We do not know how old the child actually was, any more than we know how much time elapsed between Nathan's prophecy and the child's birth.
According to the Bible, the newborn died on the seventh day after his birth.
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? (2 Samuel 12:18, KJV)
However, this was not sufficient to count, i.e. the infant would not have been numbered in a census.
And the LORD said unto Moses, Number all the firstborn of the males of the children of Israel from a month old and upward, and take the number of their names. (Numbers 3:40, KJV)
Perhaps more interesting still is that this firstborn was still below the age threshold, also a month of age, at which he could be redeemed.
And those that are to be redeemed from a month old shalt thou redeem, according to thine estimation, for the money of five shekels, after the shekel of the sanctuary, which is twenty gerahs. (Numbers 18:16, KJV)
All firstborn children were required to be redeemed. The firstborn of unclean animals were required to be redeemed--or killed. The firstborn of clean animals were required to be sacrificed, and could not be redeemed.
Sanctify unto me all the firstborn, whatsoever openeth the womb among the children of Israel, both of man and of beast: it is mine. (Exodus 13:2, KJV)
And every firstling of an ass thou shalt redeem with a lamb; and if thou wilt not redeem it, then thou shalt break his neck: and all the firstborn of man among thy children shalt thou redeem. (Exodus 13:13, KJV)
But the firstling of an ass thou shalt redeem with a lamb: and if thou redeem him not, then shalt thou break his neck. All the firstborn of thy sons thou shalt redeem. And none shall appear before me empty. (Exodus 34:20, KJV)
All the firstborn belonged to God. If a firstborn was not redeemed or not redeemable, it was killed (unclean) or sacrificed (clean).
Humans are not clean. If they are not redeemed, they would have to be killed--but redeeming them was, obviously, required. However, David did not yet have the option to redeem this firstborn because it had not yet reached the age of viability--a month of age. This is why I much appreciated the comment of @tblue, posted above, saying: "Today, death before 30 days is considered 'stillborn'. Back in the day, perhaps an infant dying before the 8th day was also considered as 'never having lived'."
True, not even circumcision would have been performed yet, as that was to be done on the eighth day. When one analyzes this carefully, and with an open mind, it can be seen as a post-natal abortion.
I’m looking at this in reproductive terms. I do believe that the baby was older than one week. Why?
- David would not have laid with Bathsheba if she was bleeding. For those that have had children we know that there is a wound in your uterus, caused by the detachment of the placenta, that will bleed.
- David laid with Bathsheba after the mourning period, which is usually seven days. She became pregnant which means she would have had to ovulate, which is not likely 14 days after giving birth.