Sita circumambulated the fire. Then, as a huge crowd looked on with wonder, she entered the flames with a fearless mind. Within the blazing fire, Sita, who was adorned with dazzling gold ornaments, shone with a golden radiance. As soon as Sita was within the flames, all the women present screamed with horror and a loud cry of anguish arose from the assembled monkeys and Rakshasas. Amidst all these sounds, Lord Ram appeared to become very thoughtful. At that time, all the principal demigods hurriedly appeared before Him, riding upon their celestial vehicles. Then, as Lord Ram stood before them, with folded hands the demigods, headed by Lord Brahma and Lord Shiva, said, "O Supreme Personality of Godhead, Lord Ramchandra, we are very pained to see how You are neglecting Your eternal consort, Mother Sita. You are the creator of the universe and the Lord of all the demigods. Why don't You recognize Your divinity instead of rejecting Sita, as if You were a common man?"
Lord Ram replied, "I consider myself to be an ordinary human being, the son of Maharaja Dasharath. But, if there is something more to be said, then perhaps you, Lord Brahma, can disclose it."
Lord Brahma then said, "My dear Lord Ram, I will now reveal Your real identity. You are directly Lord Narayana, and thus You are identical with all the forms of Vishnu-tattva. You are a plenary expansion of Lord Sri Krishna, the original Supreme Personality of Godhead, and thus You are the cause of all causes. You are the universal form, the support of the cosmic manifestation, and all of the demigods are Your parts and parcels, or in other words, Your eternal servants. Sita is none other than Lakshmi herself, the supreme Goddess of Fortune. Both of you have appeared on the earth for accomplishing the destruction of Ravan. Now that this mission has been accomplished, You may return to Your transcendental abode in the spiritual sky, after ruling over the earth for as long as You desire."
As soon as Lord Brahma finished speaking, the fire-god, Agni, emerged from the flames, carrying Sita in his arms. As Agni placed Sita before Lord Ram, everyone was amazed to see how her body, bright red dress, ornaments and hair showed absolutely no sign of being even slightly burnt.
Then, in his capacity as one of the universal witnesses, Agni announced, "Lord Ram, here is Your dear wife, Sita. She is completely pure and devoid of even the least tinge of sin. Sita was never the slightest bit unfaithful to You by word, thought or glance, and so what to speak of action. Therefore, My dear Lord Ram, You must accept Sita without reservation and give up Your harsh speech and behavior."
Lord Ram was very pleased to hear this testimony, and as tears of joy fell from His eyes, He replied, "Agni, it was necessary for Sita to undergo this trial by fire in order to convince the masses of people of her purity. If I had prevented Sita from entering the fire, people would have criticized Me for accepting her without first proving her chastity. They would have concluded that I had only taken her back because of being under the influence of lust to enjoy her."
"Actually, I knew all about Sita's purity, and I knew that Ravan could never have polluted her, for she is fully protected by the prowess of her righteousness. It was only to prove Sita's chastity to the world that I appeared to neglect her. Factually, Sita is not different from Me, for she is directly My internal potency, the hladhini-sakti. Just as sunlight, being not different from the sun, is inseparable from the sun, so there is no possibility of My rejecting Sita."
Actually, Lord Ram felt great transcendental bliss while being reunited with Sita, for His pastimes were all manifestations of His internal potency, and had been enacted for the purpose of relishing spiritual relationships.
Lord Shiva then addressed Lord Ram, saying, "My dear Lord, by slaying the incomparably powerful Ravan, You have performed a wonderful feat that will be glorified throughout the three worlds until the time of dissolution." Then, while pointing toward the sky,
Lord Shiva said, "Lord Ram, look up and see how Your father is waiting, seated upon his celestial chariot. After having been delivered by Your mercy, he now resides in the planet of Indra, the King of heaven. Go quickly, along with Lakshman, and be reunited with Maharaja Dasharath, for he has come here just to see You."
Lord Ram and Lakshman went and bowed down before Their father. Feeling extremely delighted, Maharaja Dasharath took Lord Ram on his lap and said, "My residence in heaven does not give me any real pleasure. Ram, only now that I am able to see You do I feel happy. Kaikeyi's words, demanding Your exile, have always remained imprinted on my heart. Only now that Your period of exile has ended do I feel somewhat relieved. I yearn to see Your return to Ayodhya and installed as the Emperor, after being reunited with Bharat. I can now understand that You are the Supreme Lord, Vishnu, and that You had descended upon the earth for the purpose of vanquishing Ravan."
Lord Ram replied, "My dear father, I also feel greatly relieved now that My period of exile is over and My mission has been accomplished. But still, there is one thing that I wish that you would grant Me. May you now withdraw the harsh words that you had spoken at the time of My banishment, disowning Kaikeyi and Bharat."
Maharaja Dasharath readily consented, saying, "Let it be so." Then he fondly embraced Lakshman and declared, "My dear son, because of the dedicated service that You have rendered to Ram, I feel eternally indebted to You. You should know that Your elder brother is directly the Supreme Personality of Godhead, appearing in human form, for the welfare of the world. He is worshipful even by the greatest demigods, and so what to speak of ourselves."
Maharaja Dasharath then told Sita, "Please do not bear any grudge against Ram for having tested your purity. You can rest assured that your remarkable behavior will earn you a place in history as the most glorious woman the world has ever seen."
Having thus spoken, Maharaja Dasharath remounted his celestial chariot and ascended to heaven. Then, as Lord Ram stood before him with folded hands, Indra said, "My audience can never go in vain, and so I wish that You would take a benediction from me."
Lord Ram was pleased to hear this, and He requested, "King of the celestials, please bring back to life all the monkey warriors who died in My service. In addition, let all the trees in the places where these great heroes dwell become full of fruit, even when out of season." Indra replied, "Although this boon is very difficult for even me to grant, I shall happily do so."
Immediately, all the monkeys who had died in the battle began to rise up from the ground, and since all of their wounds were completely healed, it appeared to them as if they were awakening from a deep sleep. But, when they saw Lord Ram and all the demigods before them, the monkeys could understand that they had gotten back their lost lives, and so they felt supremely delighted. Indra then ascended to heaven, followed by all the demigods.
Source
Shri Valmiki Ramayana, Yuddha-kanda