Then Haggai, the messenger of the LORD, spoke to the people with the LORD’s message: The expression the messenger of the LORD is not applied elsewhere to a prophet, though it is applied to a priest in Mal 2.7. Good News Translation has just used an identical expression in the previous verse, and does not repeat it here. It is probably better not to follow the example of Good News Translation at this point.
The change of heart by the people enabled the prophet to give them next a word of encouragement. Its content was simple: I am with you, says the LORD. The you here is of course plural. It is not clear why Good News Translation has expressed this in the future “I will be with you.” No other modern English version does this, and translators are recommended to use a present tense. The message itself was one that had often been given by the LORD to encourage his people, such as Jacob (Gen 28.15), Moses (Exo 3.12), Joshua (Josh 1.5), Gideon (Jdg 6.16), and Jeremiah (Jer 1.8).
The last part of the message says the LORD is translated in an emphatic way by Good News Translation as “that is my promise.” Other ways of expressing emphasis could be “declares the LORD” (New International Version, New Jewish Publication Society’s Tanakh) or “I, the LORD, say this” (Die Bibel im heutigen Deutsch, 2. Edition). Translators may also say, “I give you my firm promise that I am always with you.” In this case the quotation formula is part of a second degree quotation, and so it does not have a discourse level function in terms of the structure of the paragraph.
An alternative translation model for verses 12 and 13 is:
• Then Zerubbabel and Joshua the High Priest, along with all the other people who had returned from Babylonia, did what the LORD their God commanded them to do. They realized that God had sent the prophet Haggai, so they were afraid and obeyed him. Then Haggai, the messenger of the LORD, told the people that the LORD promised, “I am with you.”
Quoted with permission from Clark, David J. & Hatton, Howard A. A Handbook on Haggai. (UBS Helps for Translators). New York: UBS, 2002. For this and other handbooks for translators see here .