Was the appointing of Solomon not contrary to the law in 1 Kings 1:28-30?

Question

David appoints Solomon as King

1 Kings 1:28-30 (NKJV)

Then King David answered and said, “Call Bathsheba to me.” So she came into the king’s presence and stood before the king. 29 And the king took an oath and said, “ As the LORD lives, who has redeemed my life from every distress, 30 just as I swore to you by the LORD God of Israel, saying, ‘Assuredly Solomon your son shall be king after me, and he shall sit on my throne in my place,’ so I certainly will do this day.”

But the Law in Deuteronomy clearly states otherwise.

Deuteronomy 21:15-17 (NKJV)

“If a man has two wives, one loved and the other unloved, and they have borne him children, both the loved and the unloved, and if the firstborn son is of her who is unloved, 16 then it shall be, on the day he bequeaths his possessions to his sons, that he must not bestow firstborn status on the son of the loved wife in preference to the son of the unloved, the true firstborn. 17 But he shall acknowledge the son of the unloved wife as the firstborn by giving him a double portion of all that he has, for he is the beginning of his strength; the right of the firstborn is his.

Did not the king break the law by appointing a younger son ahead of his brothers, or was there some undue influence from Bathsheba?

Answer 1

The narrative describing the conflict leading to Solomon's succeeding to David's throne in 1 Kings 1-2 is subtle and complex. However, there is no sense that there was a rule -- let alone a "law" -- of primogeniture which would or should have prevented Solomon's ascension.

OP points to the law in Deutoronomy 21:15-17. While one might see here a connection to royal succession, that turns out to be superficial. This Deuteronomic law has its essential purpose in protecting the welfare of a vulnerable woman by ensuring her male offspring are not disinherited. This is in keeping with a theme seen across pentateuchal legislation to protect the vulnerable, especially the "widow, orphan, sojourner" set (see, e.g., Fensham or Gowan).

This has no bearing, and certainly no legal bearing, on royal succession, then. It is even contested whether or how soon or how consistently the principle of primogeniture applied to Israelite and Judaean kingship. The standard study here is F.E. Greenspahn, "Primogeniture in Ancient Israel", in Go To the Land I will Show You..., ed. by J. E. Coleson, et al (Eisenbrauns, 1996), pp. 69ff. These remarks are relevant (pp. 77-78):

Although the [Hebrew] Bible provides no explicit rules for succession to office, it does offer a wealth of insight into ancient Israelite practice. ... [However,...]
It is widely assumed that Israelite kings were normally succeeded by their oldest sons. Unfortunately, the limited amount of information in the Bible makes it impossible to achieve certainty about this issue. Of the thirty kings who succeeded to the throne in Israel and Judah, the siblings of only seven are named, usually without reference to birth order.
... The succession following David is not more supportive....

What is clear is that royal succession was not legally regulated, and the Deuteronomistic law that troubles OP is not relevant at this point.

Answer 2

I am of the opinion that king David broke the law particularly when we look at the provisions of Deut 21:15-17 but the fact that the people liked it has overruled the provisions in Deut 21:15-17. Remember the bible says the heart of the Kings are in the hand of God. If God does not support it God can stirre the heart of the people against it. The people hail the new king.