Pañcālacaṇḍasutta

sn2.7:3.1 “Even amid confinement they understand,”

sn2.7:3.2 said the Buddha to Pañcālacaṇḍa,

sn2.7:3.3 “the principle for attaining extinguishment.

sn2.7:3.4 Those who have acquired mindfulness

sn2.7:3.5 are perfectly serene in samādhi.”