The narrative in Jeremiah 32:2–5 explaining the reason for Jeremiah’s imprisonment, sets the scene for the word that came to him (Jeremiah 32:1). The reader is now told what that word is. The Lord tells Jeremiah that Hanamel the son of Shallum, Jeremiah’s uncle, will come and ask Jeremiah to buy his field at Anathoth. Hanamel comes just as the Lord said he would and Jeremiah says, Then I knew it was the word of the Lord.
It is unusual for Jeremiah to express any doubt about the Lord’s word, but it is possible that the immediate arrival of his cousin straight after the message from the Lord made it clear to Jeremiah how he should act1.
7 Behold, Hanamel the son of Shallum your uncle will come to you and say, ‘Buy my field that is at Anathoth, for the right of redemption by purchase is yours.’