Ravana tries his best to persuade Sita to become his wife. He wonders what point there is waiting for Rama. Sita is dressed in tatters, most unbecoming of her beauty, he says. He offers her all the luxuries at his disposal. If Sita were to become his wife, then she will be the foremost among all the women in his harem.
Sita scorns Ravana’s suggestions, and says that She will never succumb to his offers. Lanka has wealth and many things to commend it, but it is going to be destroyed because of the sin of one man- Ravana. He had abducted Her in a cowardly manner. He can never stand up to Rama’s might. When Ravana is killed, people will rejoice, says Sita, because the world is happy to be rid of a sinner. Sita pulls up a blade of grass and places it before Her, as if it is a barrier between Her and the demon King. And indeed the grass is a barrier, elaborated Gomatam Madhavachariar, in a discourse.
After all wasn’t a blade of grass used as an arrow by Lord Rama, when He took aim at Kakasura? That blade of grass, turned into an arrow, chased Kakasura and would surely have ended his life, if he had not sought refuge at Rama’s feet. So even a blade of grass is a potent weapon where the Lord is concerned. And Sita’s act reminds us of this incident and its import. Sita’s act of putting a grass in front of Her, is also to indicate that Ravana’s words are as insignificant as a blade of grass. It is also to indicate that he is little better than a beast that feeds on grass.
The Lord emanated from a pillar to save Prahalada. Just as He is present in a pillar, so is He present in a blade of grass, and can emerge out of anything and anywhere to save His devotees. That too is indicated by Sita’s act. So the grass that Sita places before Her, is not a mere blade of grass, but means a lot more.