Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 1: Contents of the Rāmāyaṇa Summarized
Text 1.1.80

तामुवाच ततो रामः परुषं जनसंसदि।
अमृष्यमाणा सा सीता विवेश ज्वलनं सती॥

tām uvāca tato rāmaḥ paruṣaṁ jana-saṁsadi
amṛṣyamāṇā sītā viveśa jvalanaṁ satī

tām = about her chastity; uvāca = spoke; tataḥ = therefore; rāmaḥ = Rāma; paruṣam = harsh words; jana-saṁsadi = in public; amṛṣyamāṇā = unable to tolerate them; = the; sītā = Sītā; viveśa = entered; jvalanam = fire; satī = chaste.

Therefore, Rāma spoke harsh words about her chastity in public. Unable to tolerate them, the chaste Sītā entered fire.

“In public” means “in the assembly of the demigods and others.” By speaking to her in public, Rāma indicated that Sītā should speak the truth to generate faith in her among them. Sītā was devoted to her husband alone and so she could not tolerate Rāma’s harsh words. Therefore, she entered the fire brought by Lakṣmaṇa.