Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 71: Sītā’s Noble Lineage
Text 1.71.20-21

कनीयानेष मे भ्राता अहं ज्येष्ठो महामुने।
ददामि परमप्रीतो वध्वौ ते मुनिपुङ्गव॥

सीतां रामाय भद्रं ते ऊर्मिलां लक्ष्मणाय च॥

kanīyān eṣa me bhrātā ahaṁ jyeṣṭho mahā-mune
dadāmi
parama-prīto vadhvau te muni-puṅgava

sītāṁ rāmāya bhadraṁ te ūrmilāṁ lakṣmaṇāya ca

kanīyān eṣaḥ me bhrātā = this is my younger brother; aham jyeṣṭhaḥ = and I am the elder one; mahā-mune = O great sage; dadāmi = I give; parama-prītaḥ = with extreme happiness; vadhvau te = as daughters-in-law to you; muni-puṅgava = O best of sages; sītām = Sītā; rāmāya = for Rāma; bhadram te = may there be auspiciousness unto you; ūrmilām = Ūrmilā; lakṣmaṇāya = for Lakṣmaṇa; ca = and.

O great sage, this is my younger brother and I am the elder one. O best of sages, with extreme happiness, I give Sītā for Rāma and Ūrmilā for Lakṣmaṇa as daughters-in-law to you. May there be auspiciousness unto you.

Because Vasiṣṭha asked for Janaka’s daughters, he is giving them to him as his daughters-in-law. In the next verse, he reinforces the same with reasoning.