‘ And they raised over him a great heap of stones, to this day, and YHWH turned from the fierceness of his anger, for which reason the name of the place was called the valley of Achor to this day.'
The heap of stones, partly gathered from the stones hurled in execution, was a witness (Joshua 4:21-22; Genesis 32:48). It testified to the holiness and severity of God, and yet of His mercy to the children of Israel. Compare the heap of stones piled over the body of the king of Ai (Joshua 8:29), an everlasting reminder of YHWH's triumph over disaster. And it warned of what would happen to those who treated YHWH and His covenant lightly. They remained there ‘to this day'. These constant references to ‘to this day' confirm that the Book was written not too long after the events.
“And YHWH turned from the fierceness of his anger.” Compare Deuteronomy 13:17. This language is anthropomorphic. It meant that the barrier that man had erected against God was now again broken down. Thus God no longer had to deal with them in judgment. He was able once more to show mercy and act for them without endangering man's recognition of the awfulness of sin.
“For this reason the name of the place was called the valley of Achor to this day.” ‘Achor' comes from the same root as the word for ‘trouble' in Joshua 7:25. Thus ‘the valley or plain of troubling' was a reminder of the troubling of Israel. Whether it was renamed at this time, or simply had its name given a new meaning, is unimportant. What mattered was what it meant for the future. And the name lasted ‘to this day'. Then they all returned to their camp at Gilgal.