The preposition “by” is the dative of investiture as well as means, and is Paul’s declaration that what he is writing to the Thessalonians are not his ideas, clothed in his own language, but ideas and thoughts whose investiture, whose very clothing, is no less than the word of the ascended Lord—he who is none other than the “Word of God.”
Writing to the Corinthians he says:
“Which things we speak, not in the words which man’s wisdom teacheth, but (and grammar requires us to understand) in the words which the Holy Ghost teacheth.” (1 Corinthians 2:13.)
According to Paul’s testimony, therefore, the fourteen epistles which he wrote to the churches are not letters written by a mortal man, giving expression to the ideas and thoughts of man, but are the very words of the infinite God, giving utterance by the Holy Ghost to the thoughts of God.
An examination of the other epistles of the New Testament will show the same high and unqualified pretension. The apostles write (all of them) not as men who are giving an opinion of their own, but as men who know themselves under the domination of the Spirit, and as giving authoritative expression to the mind and will of God.
Nor is this peculiar to the writers of the New Testament.
Constantly, the writers of the Old Testament introduce their message with the tremendous sentence: “Thus saith the Lord.” Again and again they declare the Lord has spoken “by” them. David says: “The words of the Lord were in my tongue.” Jeremiah says the Word of the Lord came to him and the Lord said: “Take a roll of a book and write therein all the words that I have spoken to thee.” Then we are told that “Jeremiah called Baruch, the son of Neriah; and Baruch wrote from the mouth of Jeremiah all the words of the Lord, which he had spoken unto him, upon a roll of a book.”
After these words had been read to the princes of Israel, they asked Baruch, saying, “Tell us now, how didst thou write all these words at his mouth?” Then Baruch answered them, “He pronounced all these words unto me with his mouth, and I wrote them with ink in the book.”
The process is clear enough. The Lord spake his words in Jeremiah. Jeremiah received the words direct from the Lord, dictated them word for word to Baruch, Baruch wrote them as they were pronounced in a book; and when written, the words were the written words of God.
Ezekiel declares when the Lord commanded him to speak to the children of Israel, he said to him: “Speak with my words unto them.” Ezekiel not only speaks them, he writes them in the book of his prophecy. Ezekiel gives an account of how the Lord spake to him and inspired the book which bears his name. He says: “The Spirit entered into me when he spoke to me; . . . the spirit entered into me and spake with me.” The Spirit said unto him: “When I speak with thee, I will open thy mouth, and thou shalt say unto them, thus saith the Lord.”