According to the description found in the Sundara Kanda of Shri Ramcharitmanas; while searching for Mata Sita, Hanuman Ji reaches Lanka. There, he meets Vibhishan Ji. After introducing himself and inquiring about well-being from Vibhishan Ji, Hanuman Ji says - "O brother! I wish to have Darshan of Mata Janaki." Then Vibhishan Ji described to Hanuman Ji the condition in which Mother Sita was in Lanka and the place where She was residing. Vibhishan Ji explained all the methods to have Darshan of Mata. After learning about Mata Sita from Vibhishan Ji, Hanuman Ji took leave from him and assumed a tiny form like Masaka, i.e., a mosquito and proceeded towards that area of Ashokavan where Mother Sita was seated.
Hanuman Ji saw that in a garden situated in Ashokavan; Goddess Sita was seated. Upon seeing Her, Hanuman Ji mentally bowed to Her. Mata Sita's body had become weak and frail. On Her head, there was a braid of matted hair. She constantly remained absorbed in remembering Shri Raghunath Ji in Her heart. Sitting in the same place, She spent all four Prahara of the night.
Shri Janaki Ji kept Her eyes fixed on Her feet and looked downward, while Her mind was absorbed in the lotus feet of Shri Rama. Seeing Janaki Ji in such a miserable and sorrowful condition, Pavanputra Hanuman Ji became extremely distressed. Hiding among the leaves of the Ashoka tree, Hanuman Ji began to think while watching Mata, O Lord! What should I do? How can I relieve Mata's suffering?" At that very moment, Ravana, the king of Lanka, arrived there, adorned and accompanied by many women. That wicked Ravana began to persuade Sita Ji in various ways through conciliation, gifts, fear, and deceit.
Ravana said to Devi Sita - "O beautiful-faced one! I will make Mandodari and all my queens your servants, this is my vow. Just look at me once."
Remembering Her most beloved Lord Shri Ramachandra Ji, Janaki Ji placed a blade of grass in between and said - "O Dashamukha! A lotus cannot bloom by the light of a firefly. If my Lord is like Surya, then you are merely a firefly. You are not yet acquainted with the strength of Shri Raghunath Ji's arms."
Hearing the harsh words of Devi Sita and hearing himself compared to a firefly while Shri Ramachandra Ji was compared to the Surya, Ravana, in anger, drew his weapon and said - "Sita! You have insulted me. I will cut off your head with this sword. Accept my proposal immediately, otherwise your life will end."
Mata Sita said - "O Dashagriva! Either the beautiful and mighty arms of my Lord will be around my neck, or your dreadful sword. O wicked one! This is my firm resolve."
Hearing Sita Ji's words, Ravana rushed towards Her to attack. At that moment, Ravana's righteous wife Mandodari restrained him with wise counsel. Thereafter, Ravana ordered the fierce demonesses and said - "O demonesses! Torture this Sita in various ways and frighten her. If she does not accept my proposal within one month, I will kill her." Saying this, Ravana went to his palace, and all the demonesses assumed terrifying forms and began to frighten Sita Ji.
Among those demonesses was one named Trijata, who was very wise. She was a devoted follower of Shri Ramachandra Ji. Narrating a dream to everyone, Trijata said - "Serve Sita Ji and ensure your welfare. I saw in my dream that a monkey burned Lanka and destroyed the entire army of the demons. Ravana was naked, without hair, riding on a donkey, and all his twenty arms were severed. In this condition, Ravana was proceeding towards the southern direction, towards Yamapuri, i.e., the abode of Yama, and the kingdom of Lanka had been obtained by Vibhishan. In the city, the name of Shri Ramachandra Ji was being proclaimed, and He had sent for Sita Ji. I say with certainty that this dream will come true within four days."
Hearing Trijata's words, all the demonesses became frightened and began to bow at the feet of Janaki Ji. Sita Ji began to think in Her mind that after one month, that wicked demon Ravana would kill Her.
Folding Her hands, Sita Ji said to Trijata - "O Mata! You are the companion in my distress. Please quickly find a way by which I may give up my body. This separation has become unbearable for me. Bring some wood from somewhere and prepare my funeral pyre. O Mata! Then light a fire in it. In this way, fulfill my love. I cannot endure the piercing words of Ravana, which are like a spear."
Hearing Sita Ji's words, Trijata held Her feet and consoled Her, glorifying the power, strength, and fame of the Lord. She said - "O delicate one! Listen, fire cannot be obtained at night." Saying this, she went to her home.
Sita Ji began to think within Herself - "O Lord! What should I do? Fate has turned adverse. Neither will I get fire, nor will my pain end. O Ashoka tree! Hear my request! Remove my sorrow and make your name Ashoka, i.e., remover of sorrow true. Your fresh tender leaves are like fire. Give me fire and end this agony of separation; do not let this pain of separation increase to its extreme."
Seeing Sita Ji so distressed in separation, Hanuman Ji felt deep pain. Then, after thinking in his heart, he dropped Shri Rama's ring in front of Mata Sita. Devi Sita thought that the Ashoka tree had given a spark and happily picked up the ring.
Mata Sita saw the beautiful and charming ring engraved with the name of Rama. Recognizing it, Sita Ji became astonished and began to look at it. Her heart was filled with both joy and sorrow. She began to think that Shri Raghunath Ji is invincible, who could defeat Him? And it is impossible to create such a ring by illusion. Sita Ji was contemplating many such thoughts in Her mind.
At that very moment, Hanuman Ji, seated on the Ashoka tree, began to describe the virtues of Shri Ramachandra Ji in a sweet voice. Hearing Rama Katha, i.e., the glory of Shri Rama, Sita Ji's sorrow was removed. She began to listen attentively to the Rama Katha with full concentration. Hanuman Ji narrated the entire story of Rama from the beginning.
After hearing the Katha, Mata Sita said - "O brother! The one who has narrated this beautiful, nectar-like story, why does he not appear before me?" Hearing this, Hanuman Ji appeared before Her. Upon seeing Hanuman Ji, Sita Ji again turned Her face away and sat. Seeing this, Hanuman Ji felt surprised.
At that time, Hanuman Ji said - "O Mata Janaki! I am the messenger of Shri Rama. I swear to my Lord that I have brought this ring. Shri Rama has given me this as a token for you."
Mata Sita, expressing curiosity, asked - "O child! How did the association between a human and a Vanara take place? How did you meet Shri Rama?" Then Hanuman Ji narrated the entire account of his meeting with Shri Rama. Hearing the affectionate words of Hanuman Ji, Sita Ji developed faith in her heart. She understood that Hanuman Ji is the servant of Shri Raghunath Ji by mind, action, and speech.
When Hanuman Ji presented Shri Rama's ring to Mata Sita in Ashoka Vatika, that day was the auspicious Ashtami of the Shukla Paksha of the Chaitra month. From that very time, this day became famous in all the worlds as Ashoka Ashtami. On this day, the Ashoka tree is worshipped and a Vrat is observed. In this Vrat, the buds of the Ashoka tree are consumed. According to beliefs, drinking the juice of Ashoka buds on this day destroys all diseases of the body.
॥Thus concludes the Ashoka Ashtami Vrat Katha described in Shri Ramcharitmanas॥