Valmiki Ramayana Ayodhya Kanda Sarga 21 Shloka 48

त्वया by you, मया च by me, वैदेह्या by Sita, लक्ष्मणेन by Lakshmana, सुमित्रया by Sumitra, पितुः father's, नियोगे by the orders, स्थातव्यम् we shall abide, एषः this alone, सनातनः eternal, धर्मः law.

You, Sita, Lakshmana, Sumitra and I -- all of us shall abide by the words of my father. This indeed is eternal law.