The prophet who has predicted peace, if his word will occur, then the prophet will be known as one whom the Lord has sent in truth.
Other versions
King James Version
The prophet which prophesieth of peace, when the word of the prophet shall come to pass, then shall the prophet be known, that the LORD hath truly sent him.English Standard Version
As for the prophet who prophesies peace, when the word of that prophet comes to pass, then it will be known that the LORD has truly sent the prophet."New International Version
But the prophet who prophesies peace will be recognized as one truly sent by the LORD only if his prediction comes true."