Albert Barnes Commentary Lamentations 1:21

"They have heard that I sigh; there is none to comfort me; All mine enemies have heard of my trouble; they are glad that thou hast done it: Thou wilt bring the day that thou hast proclaimed, and they shall be like unto me." — Lamentations 1:21 (ASV)

They have heard ... - Or, They heard that I sigh, that I have no comforter.

Thou wilt bring the day ... - literally, you have brought the day thou hast proclaimed, and they shall be like unto me. The day of Judah’s punishment was the proof that the nations now triumphing over Jerusalem’s fall would certainly be visited.