Canto 2 -
Ayodhyā-kāṇḍa
Chapter 106: Bharata Persists in His Request
Text 2.106.9

धर्मबन्धेन बद्धोऽस्मि तेनेमां नेह मातरम्।
हन्मि तीव्रेण दण्डेन दण्डार्हां पापकारिणीम्॥

dharma-bandhena baddho ’smi tenemāṁ neha mātaram
hanmi tīvreṇa daṇḍena daṇḍārhāṁ pāpakāriṇīm

dharma-bandhena = by the noose of dharma; baddhaḥ = bound; asmi = I am; tena = therefore; imām = this; na = cannot; iha = here; mātaram = mother of mine; hanmi = I kill; tīvreṇa = severe; daṇḍena = as a punishment; daṇḍa-arhām = and deserves to be punished; pāpakāriṇīm = [though] she has committed a sin.

I am bound by the noose of dharma. Therefore I cannot kill, as a severe punishment, this mother of mine here [though] she has committed a sin and deserves to be punished.