Matthew Poole and continuators on Jeremiah 29:3

3 By the hand of Elasah the son of Shaphan, and Gemariah the son of Hilkiah, whom Zedekiah king of Judah sent unto Babylon to Nebuchadnezzar king of Babylon, saying .

Zedekiah the King of Iudah having some occasion to send two messengers, named Elasa and Gemariah to Babylon, whether to carry his tribute money, or upon what other errand is not expressed. Ieremiah knowing that as there were some false Prophets at Ierusalem, who fed people with hopes of a speedy return, so there were some with them in Babylon, who did the like, (two of which he afterwards in this Chapter reflecteth upon) writeth the following letter, and sends it by these two messengers, to quiet the peoples minds, and to help to compose their spirits, disturb'd by these false Prophets, and raised up to vain and idle hopes for which there was no ground at all.