tam jahara dasa-grivah
sita vahni-puram gata
chaya-sita vivesa sa
vahnih sitam samaniya
sitaya—by mother Sita; aradhitah—being called for; vahnih—the fire-god; chaya-sitam—the illusory form of mother Sita; ajijanat—created; tam—her; jahara—kidnapped; dasa-grivah—the ten-faced Ravana; sita—mother Sita; vahni-puram—to the abode of the fire-god; gata—departed; pariksa-samaye—at the time of testing; vahnim—the fire; chaya-sita—the illusory form of Sita; vivesa—entered; sa—she; vahnih—the fire-god; sitam—the original mother Sita; samaniya—bringing back; tat-purastat—in His presence; aninayat—brought back.
"When he was petitioned by mother Sita, the fire-god, Agni, brought forth an illusory form of Sita, and Ravana, who had ten heads, kidnapped the false Sita. The original Sita then went to the abode of the fire-god. When Lord Ramacandra tested the body of Sita, it was the false, illusory Sita that entered the fire. At that time the fire-god brought the original Sita from his abode and delivered her to Lord Ramacandra."
Link to this page: https://prabhupadabooks.com/cc/madhya/9/211-212