Albert Barnes Commentary 2 Kings 14:7

"He slew of Edom in the Valley of Salt ten thousand, and took Sela by war, and called the name of it Joktheel, unto this day." — 2 Kings 14:7 (ASV)

Amaziah’s war with Edom is described in detail by the writer of Chronicles.

The “Valley of Salt” is usually identified with the broad, open plain called the Sabkah at the southern end of the Dead Sea, which is a continuation of the Ghor, or Jordan Valley gorge. A mountain of rock salt stands at the northwestern corner of this plain, and the area between this mountain and the sea is a salt marsh. Salt springs are also abundant in the plain itself, which would fully account for the name.

However, it is doubtful that the original Hebrew word for “valley,” which is commonly used for clefts and ravines, can be applied to a sunken plain like the Sabkah. Furthermore, it is highly unlikely that 10,000 prisoners would have been transported more than eighty miles—the distance from the Sabkah to Petra—through rough and difficult country, only to be massacred.

On the whole, it is more probable that the “Valley of Salt” has not yet been discovered and that its true location was near Selah or Petra (see the note on Judges 1:36). In a spirit of religious devotion, Amaziah renamed Petra to Joktheel, meaning “subdued by God,” to acknowledge the divine aid that gave him the victory. The name did not remain in use, however, because when the Edomites recovered their city not long afterward, they restored its original name (2 Chronicles 28:17; compare to Isaiah 16:1 and Amos 1:11).

Unto this day—The writer of Kings is evidently quoting his source document directly. This source must have been composed no later than the reign of Ahaz, since the Edomites had recovered Petra before Ahaz’s death.