Valmiki Ramayana Ayodhya Kanda Sarga 52 Shloka 61
Original Shlokaनगरीं त्वां गतं दृष्ट्वा जननी मे यवीयसी। कैकेयी प्रत्ययं गच्छेदिति रामो वनं गतः।।2.52.61।।
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नगरीम् to the city of Ayodhya, गतम् gone, त्वाम् you, दृष्ट्वा on seeing, मे my, यवीयसी younger, जननी mother, कैकेयी Kaikeyi, रामः Rama, वनम् to the forest, गतः had gone, इति thus, प्रत्ययम् conviction, गच्छेत् will have.
When my younger mother Kaikeyi sees that you have returned to Ayodhya, she will believe that Rama has really gone to the forest.