Sundarakānda - Canto 21

Placing a blade of grass between herself and Rāvana in order to avoid direct contact with a man of evil intentions and expostulating with him by showing him the right path, Sītā praises Śrī Rāma and, impressing on Rāvana the consequences of the latter befriending or antagonizing Śrī Rāma, advises Rāvana to make friends with Śrī Rāma through self-surrender.