expression
lifelong devotion to ascetic practice
A Buddhist term referring to the commitment to pursue ascetic training throughout one's entire life.
彼は一生精進を誓い、山にこもった。
He vowed lifelong devotion to ascetic practice and secluded himself in the mountains.
Compound of 一生 (lifetime) and 精進 (ascetic devotion, diligence). The exact historical derivation is uncertain; the expression is primarily used in Buddhist contexts.