Now the word of the LORD came to me, saying,
Here is, I. A command given to Jeremiah to go and carry a message from God to the inhabitants of Jerusalem. He was charged in general (Jer 1:17) to go and speak to them; here he is particularly charged to go and speak this to them.
Commenting on Jeremiah 2:1-8
Moreover, the word of the Lord came to me, saying. Here begins the book, and Jeremiah's first sermon; and the following contains the message he was sent with, to which the preceding chapter is only a preface or introduction. The Targum calls it, "the word of the prophecy from before the Lord.''
If we compare the six longer discourses in these chapters with the sayings and prophecies gathered together in the other portions of the book, we observe between them this distinction in form and matter, that the former are more general in their character than the latter.
Commenting on Jeremiah 2:1-3