Albert Barnes Commentary Haggai 1:3

"Then came the word of Jehovah by Haggai the prophet, saying," — Haggai 1:3 (ASV)

And the word of the Lord came - “Before, he prophesied nothing, but only recited the saying of the people; now he refutes it in his prophecy, and repeats, again and again, that he says this not from himself, but from the mind and mouth of God.” It is characteristic of Haggai to emphasize so frequently that his words are not his own, but the words of God.

Yet “the prophets, both in their threats and prophecies, repeat again and again, Thus saith the Lord, teaching us how we should value the word of God, cling to it, keep it always in our mouth, reverence, meditate on, utter, praise it, and make it our continual delight.”