Valmiki Ramayana Ayodhya Kanda Sarga 14 Shloka 22
Original Shlokaस्थाप्य राज्ये मम सुतं कृत्वा रामं वनेचरम्। निस्सपत्नां च मां कृत्वा कृतकृत्यो भविष्यसि।।2.14.22।।
1 source checked for this shloka
मम सुतम् my son, राज्ये in the kingdom, स्थाप्य having installed, रामम् Rama, वनेचरम् a forestor, कृत्वा having made, माम् me, निःसपत्नाम् devoid of rivals, कृत्वा having made, कृतकृत्यः भविष्यसि you will have fulfilled your duty.
Only after you have installed my son in the kingdom and sent Rama to the forest and made me free from rivals, you shall have your duty fulfiled.