Charles Ellicott Commentary Jeremiah 27:18

"But if they be prophets, and if the word of Jehovah be with them, let them now make intercession to Jehovah of hosts, that the vessels which are left in the house of Jehovah, and in the house of the king of Judah, and at Jerusalem, go not to Babylon." — Jeremiah 27:18 (ASV)

But if they be prophets ... —The rivals of Jeremiah had, as has been said, staked their credit upon the return of the vessels that had already been taken. He stakes his on the prediction that what had been spared in the first invasion should be taken in the second. They had better use their gift of the Spirit, if they had any, in interceding for their preservation.