Charles Ellicott Commentary Jeremiah 29:28

"forasmuch as he hath sent unto us in Babylon, saying, [The captivity] is long: build ye houses, and dwell in them; and plant gardens, and eat the fruit of them?" — Jeremiah 29:28 (ASV)

This captivity is long ... —As the italics show, there is no word corresponding to “captivity” in the Hebrew, and some commentators render the words, It is far off ... as though Jeremiah had counted on the distance of Babylon as enabling him to write the letter with impunity, or possibly in all the emphasis of abruptness. “All is a long way off—the end of your exile, your present distance from your native land, and haste, therefore, is but folly.”