Srimad Bhagavatam Canto 01, Chapter 07, Text 33

SB 1.7.33

tata asadya tarasa
darunam gautami-sutam
babandhamarsa-tamraksah
pasum rasanaya yatha
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
Arjuna, his eyes blazing in anger like two red balls of copper, dexterously arrested the son of Gautami and bound him with ropes like an animal.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
Asvatthama’s mother, Krpi, was born in the family of Gautama. The significant point in this sloka is that Asvatthama was caught and bound up with ropes like an animal. According to Sridhara Svami, Arjuna was obliged to catch this son of a brahmana like an animal as a part of his duty (dharma). This suggestion by Sridhara Svami is also confirmed in the later statement of Sri Krsna. Asvatthama was a bona fide son of Dronacarya and Krpi, but because he had degraded himself to a lower status of life, it was proper to treat him as an animal and not as a brahmana.
 
Srimad Bhagavatam Canto 01, Chapter 07, Text 32
Srimad Bhagavatam Canto 01, Chapter 07, Text 34