unshakable faith and strict practice
A yojijukugo describing a person whose religious or spiritual conviction is firm and whose conduct is disciplined. Often used in Buddhist contexts.
He is a monk of unshakable faith and strict practice.
With a spirit of unwavering devotion, he devotes himself to daily training.
A yojijukugo composed of 道心 (religious mind, devotion) and 堅固 (firm, steadfast). The exact historical derivation is uncertain, but it is conventionally associated with Buddhist ideals of unwavering faith and rigorous practice.