Devibhagavatapurana 3.21.45

3.21.45

tathāhamapi tanvaṅgi karomyadya durāsadam |
vivādo yena rājñāṃ vai kṛte sati śamaṃ vrajet ||

I will also put forward a pawn very difficult to be carried out, as Janaka originally made an offer of the hands of Sitâ to whomsoever, who would break the S’iva’s strong bow. Thus the quarrels amongst the kings might be diminished; for he who will be able to fulfill the promise, will be able to accept you. Then, be he Sudars’ana or any other king, whoever will be strong to fulfill the promise will take you as his wife.