When Hanuman reached Lanka, he saw Sita being tortured by the rakshasis. Hanuman thought it was important to assure Sita of her safety.
After the raksahasis had left, Hanuman came out of hiding. Thinking that Sita might mistake him as Ravana's man, he narrated Ram's story and showed her his ring. Sita was overjoyed, but she also reminded Hanuman that only two months were left before Ravana would kill her.
At this hanuman begged to take Sita across the ocean but Sita replied that Rama should himself come and take her back after defeating Ravana.
Hanuman promised her of their return. As he prepared to go, Sita handed over her jewellery to him as a token of her love for Rama.