The “Biblical Appeal to Precedent” is one of the most common justifications LDS use for Joseph Smith introducing the practice of Polygamy. But I don’t find the argument that “they did it in the Bible” to be convincing. Here’s why:
– The prophets of the Bible may have been committing error in their practice.
– The Bible may be incorrectly reporting the details of their polygamy.
– The Prophets of the Bible never denied their polygamy, or kept if from their first wives (that we know about, of course).
– The Prophets of the Bible never took women who were married to other men. Obviously, the incident with David and Bathsheba comes to mind, and we know how God felt about that.
– The polygamy of the Bible may have been a cultural practice only, such as slavery. The fact that God apparently tolerated something thousands of years ago doesn’t necessarily argue for its status as a doctrine or divinely instituted practice.
I think it’s interesting to read about Biblical polygamy, but when I consider Joseph Smith’s practice of the practice, I find it largely irrelevant (other than suggesting a possible inspiration for Joseph’s institution of the practice in the first place.)
So if you insist on trying to explain why Joseph Smith introduced polygamy, please stick with the only answer you can be sure about: Joseph Smith thought God had commanded him to do it. Anything beyond that and you may find yourself in argumentatively dubious waters.