Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 31: Viśvāmitra, Rāma and Lakṣmaṇa Depart for Mithilā
Text 1.31.6

मैथिलस्य नरश्रेष्ठ जनकस्य भविष्यति।
यज्ञः परमधर्मिष्ठस्तस्य यास्यामहे वयम्॥

maithilasya nara-śreṣṭha janakasya bhaviṣyati
yajñaḥ
parama-dharmiṣṭhas tasya yāsyāmahe vayam

maithilasya = the king of Mithilā; nara-śreṣṭha = O best of men; janakasya = by Janaka; bhaviṣyati = is to be performed; yajñaḥ = a sacrifice; parama-dharmiṣṭhaḥ = supremely in line with Vedic dharma; tasya = that; yāsyāmahe vayam = we will go to attend.

O best of men, a sacrifice supremely in line with Vedic dharma is to be performed by Janaka, the king of Mithilā. We will go to attend that.

The sacrifice was supremely in line with Vedic dharma for it was conducted by Janaka as a service to the Supreme Personality of Godhead and so was superior to Vedic rituals that were either prescribed to be performed daily or recommended to be performed for the fulfillment of material desires.

NOTE. King Janaka of Mithilā demonstrated how to perform one’s prescribed duties in full consciousness of the Supreme Personality of Godhead. This is mentioned by the Lord Himself in Bhagavad-gītā (3.20):

karmaṇaiva hi saṁsiddhim āsthitā janakādayaḥ
loka-saṅgraham
evāpi sampaśyan kartum arhasi

“Kings such as Janaka attained perfection solely by performance of prescribed duties. Therefore, just for the sake of educating the people in general, you should perform your work.”