Canto 3 -
Araṇya-kāṇḍa
Chapter 70: The Fall of Kabandha

Lakṣmaṇa told Rāma that since Kabandha was incapable of fighting back, They shouldn’t kill him; instead, They should just cut off his arms. When Kabandha heard that, he grabbed Them and was about to put Them into his mouth when They cut off his arms. When Kabandha fell on the ground, he asked Them about Their identities. Lakṣmaṇa informed him of all events up to the abduction of Sītā-devī and then asked Kabandha about his identity and how he got such a form.