1,700 horsemen
Then David defeated Hadadezer, the son of Rehob king of Zobah, as he went to restore his rule at the River. 4 David captured from him 1,700 horsemen and 20,000 foot soldiers; and David hamstrung the chariot horses, but reserved enough of them for 100 chariots.
NASB  2 Samuel 8:3-4

7,000 horsemen
David also defeated Hadadezer king of Zobah as far as Hamath, as he went to establish his rule to the Euphrates River. 4 David took from him 1,000 chariots and 7,000 horsemen and 20,000 foot soldiers, and David hamstrung all the chariot horses, but reserved enough of them for 100 chariots.
NASB  1 Chronicles 18:3-4

SAB Contradiction 223

An old problem

Did David capture 1,700 or 7,000  horsemen from Hadadezer to restore his rule at the River Euphrates? A serious discrepancy between 2 Samuel and 1 Chronicles?
From antiquity onwards, a lot has already been done to bring the different numbers of these texts into agreement. The Septuagint, (old Greek translation, approximately 2nd century B.C.), translated it as ‘7,000 riding-horses’ instead of ‘7,000 horsemen’. And so the discrepancy between 7,000 horsemen (1 Chronicles) and 1,700 horsemen (2 Samuel) disappeared. Flavius Josephus says about the cavalry 'approximately 5,000'; so he didn't want to commit himself.

A little copying error?

In the last ages, one has generally accepted the possibility of copying errors by scribes. However in all those cases where this assumption has been made by modern exegetes,not one single inconsistency that should show a copy error is to be found in the delivered Hebrew texts. It has become a general way of escape among theologians if they don’t  know to explain a text. For that reason there is also a call nowadays among scholars to accept the text as it is, without trying to harmonize this contradiction, as it is only a small inconsistency.

Classic Bible reading

Indeed we should take these texts as they are, but without accepting all sorts of copying errors. That is the classic way of reading the Bible. That means that theology has the task to explain difficulties, instead of accepting them as discrepancies. It is beneath the dignity of theology to be content with less. The theological disposition to harmonize what doesn’t fit, or the custom of assuming a copyist error in case of a synoptic question, only show incomprehension and narrowness of mind.

How did David’s writers read?

How did the prophetical authors look at these reports in David’s time? That’s the central question here. They knew that reports of acts of war often represented several moments of observation: generally one of the battlefield and one after the pursuit. Obviously 2 Samuel reported the first confrontation, as it offers the smaller numbers. The capturing of 20,000 foot soldiers certainly referred to a massive surrender already at the beginning of the fight. From the second report (1 Chronicles) they learned that a large group of riders escaped after the first confrontation and had been taken later on during the pursuit.

No contradiction at all

Is it artificial to solve this old ‘Bible inconsistency’ in this way? Isn’t it too simple? No, these texts came into being in a prophetical culture with great respect for truth. Notes represented the impressions of the moment and kept their importance. From that perspective it is understandable that the books of Samuel and Chronicles refer to each other nearly constantly. And so it is a must to read them as complementary, as we have done. No contradiction at all.

No Bible Contradiction