Valmiki Ramayana Ayodhya Kanda Sarga 29 Shloka 10

प्रिय O beloved Rama, मया by me, वनवासस्य to dwell in the forest, सः आदेशः such orders, प्राप्तव्यः किल certainly needs to be obtained, सा अहम् such I am, त्वया सह along with you, तत्र there, यास्यामि I shall accompany, अन्यथा न not otherwise.

Therefore, O my beloved I must certainly obtain such a command to dwell in the forest. I must accompany you to the forest and it cannot be otherwise.