Charles Ellicott Commentary Jeremiah 31:16

"Thus saith Jehovah: Refrain thy voice from weeping, and thine eyes from tears; for thy work shall be rewarded, saith Jehovah; and they shall come again from the land of the enemy." — Jeremiah 31:16 (ASV)

Your work shall be rewarded, says the Lord. —Literally, there-shall be a reward for your work. The words are a reproduction of the old prophecy of Azariah, the son of Oded (2 Chronicles 15:7). Rachel, personifying the northern kingdom, perhaps even the collective unity of all Israel, is thought of as labouring in the work of repentance and reformation, as with a mother’s care, and is comforted with the thought that her labour shall not be in vain. This seems a more satisfactory interpretation than that which refers the “work” of the weeping Rachel to the travail of childbirth.