Some argue that the Bible is contradictory concerning how many horsemen David captaured. The argument is that 2 Samuel 8:4 says that David captured 1,700 horsemen, but 1 Chronicles 18:4 says that he captured 7,000 horsemen. However, there is a reasonable explanation that solves this alleged contradiction in the Bible.
And David took from him 1,700 horsemen, and 20,000 foot soldiers. And David hamstrung all the chariot horses but left enough for 100 chariots.2 Samuel 8:4 (KJV)
And David took from him 1,000 chariots, 7,000 horsemen, and 20,000 foot soldiers. And David hamstrung all the chariot horses, but left enough for 100 chariots.1 Chronicles 18:4
Geisler and Howe say this:
Probably on earlier copyist inadvertently omitted the word “chariot” that we find supplied in some translations. This in turn created a problem for a later copyist who would have recognized that it was not proper Hebrew structure to write “one thousand seven thousand” horsemen,” so he would have reduced the second “thousand” to “hundred” resulting in the reading we now have in 2 Samuel 8:4.Geisler, Norman and Thomas Howe, ”When Critics Ask”, p. 171-172.
Thus, the correct manuscript is probably 1 Chronicles 18:4, and 2 Samuel 8:4 contains a copyist error.
There are some foundational principles that apply to all alleged and apparent contradictions in the Bible. To read more, see Bible Difficulties: Foundational Principles.
To read more answers to alleged and apparent contradictions in the Bible, see “Contradictions” in the Bible Answered.
These books are also excellent resources: