Rama smiled and replied, "Fair maiden, you are indeed very beautiful, but I am a married man and I cannot take more than one wife. Please go and ask My brother, Lakshmana, to marry you. He is alone and without a wife in the forest. He is also very handsome, brave and strong. He will make a better husband for you."
Shurpanakha then saw Lakshmana and said, "Yes, You are also so handsome. Marry me and we will live here very happily."
Lakshmana understood that Rama was only joking but that Shurpanakha was taking Him seriously. So He decided to play up with Rama's joke. He said, "I am only the servant of My great and powerful brother. I will not be able to make you as happy as He can."
So Shurpanakha went back to Rama and said, "Because You have this ugly skinny woman for Your wife, You do not want to marry me. I will eat Her up this moment and then I will make You my husband!"
Shurpanakha's eyes were red with anger. She stepped forward towards Sita. Seeing this, Sita became afraid. Rama saw Her fear and said to Lakshmana, "It is not good to sport with wicked people. Please take care that Sita is not harmed. This Rakshasi has to be punished. Cut off her ears and chase her away!"
Lakshmana jumped before the Rakshasi and cut off the tips of her nose and ears. Screaming with pain, Shurpanakha ran to her brother Ravana. She told him of all that had happened. Seeing his sister bleeding and in pain, Ravana got ready to find Rama and Lakshmana and kill Them. Shurpanakha said to her brother, "I have seen the beautiful wife of Rama, the son of King Dasharatha of Ayodhya. She looks like an angel and will make the perfect wife for you. I tried to capture Her and bring Her here for you but look what Rama's brother did to me! You must go yourself and get Sita, and make Her your wife. It will be very easy for you to do this."
Hearing of the beauty of Sita, Ravana decided to go immediately and get Her. He took the help of Maricha, the Rakshasa whom Rama had spared when he was guarding Vishwamitra's hermitage. Maricha was a demon with powers to change his form as he pleased, so he took the form of a golden deer.
Grazing on the grass that grew outside the hermitage of Rama, while Sita went about Her work, Maricha made sure that the princess saw him. When Sita set Her eyes on the golden deer, She was so attracted to it that She wanted to keep it as a pet.
She tried to catch it by giving it grass but it kept slipping away from Her reach. Sita then knew that She would need help. So She said to Rama, "This golden deer is so beautiful! It would make such a nice pet for Me. Could You please catch it for Me?"
Rama then spoke to Lakshmana, "Dear brother, I will chase this deer and catch it for Sita. It is indeed very beautiful. You stay here and protect Sita while I am gone."
But Lakshmana was not happy. "O Rama, best among men! This is not a deer, but a demon in disguise. Maricha has his dwelling nearby and must have changed his form to attract Us and cause mischief. Please do not go after this deer."