"The Lord then commanded Jeremiah to write letters to the captains, elders, priests, prophets, and all the people who had been taken as captives to Babylon, bidding them not to be deluded into believing their deliverance nigh, but to quietly submit to their captors, pursue their vocations, and make for themselves peaceful homes among their conquerors. The Lord bade them not to allow their prophets or diviners to deceive them with false expectations; but He assured them by the words of Jeremiah that after seventy years of bondage they should be delivered and return to Jerusalem. He would listen to their prayers and give them His favor when they turned to Him with all their hearts. “And I will be found of you, saith the Lord: and I will turn away your captivity, and I will gather you from all the nations, and from all the places whither I have driven you, saith the Lord; and I will bring you again into the place whence I caused you to be carried away captive.” 4T 172.2"
"Thus saith the Lord of hosts, the God of Israel, unto all that are carried away captives, whom I have caused to be carried away from Jerusalem unto Babylon;"
The EGW passage directly references and quotes Jeremiah 29:4 regarding the letter sent to the captives in Babylon.