This is a quotation from the Raghu-vaṁśa (14.46). Lord Rāmacandra’s statement to Sītā given below is from the Rāmāyaṇa (Ayodhyā-kāṇḍa 22.9).
When Laksmana, the younger brother of Lord Ramacandra, heard of this, He immediately engaged Himself in the service of His elder brother and accepted His orders. The order of the spiritual master must be obeyed without consideration
Expressions researched:
"When Lakṣmaṇa, the younger brother of Lord Rāmacandra, heard of this, He immediately engaged Himself in the service of His elder brother and accepted His orders. The order of the spiritual master must be obeyed without consideration"
Sri Caitanya-caritamrta
CC Madhya-lila
“‘Being ordered by his father, Paraśurāma killed his mother, Reṇukā, just as if she were an enemy. When Lakṣmaṇa, the younger brother of Lord Rāmacandra, heard of this, He immediately engaged Himself in the service of His elder brother and accepted His orders. The order of the spiritual master must be obeyed without consideration.’.
“‘Being ordered by his father, Paraśurāma killed his mother, Reṇukā, just as if she were an enemy. When Lakṣmaṇa, the younger brother of Lord Rāmacandra, heard of this, He immediately engaged Himself in the service of His elder brother and accepted His orders. The order of the spiritual master must be obeyed without consideration.’