Immutable Energy
Vīrya ('valor,' 'energy,' 'immutable vigor') is the quality by which Brahman remains unchanged — unexhausted and unaffected — even while sustaining all of creation. A human craftsman grows tired after creating; a human ruler weakens from governing; Brahman, possessing vīrya, creates and sustains the infinite universe without any expenditure of effort or diminution of His own being.
Vīrya as Invulnerability
The term also carries the sense of invulnerability — the Lord cannot be harmed, diminished, or overcome by any force. Unlike the gods (devas) who can be weakened, overthrown, or limited, Brahman's vīrya means He is invulnerable to all challenge. This is part of why He alone is the fit refuge: only the invulnerable can offer true protection.
Relationship to Bala
Vīrya is related to bala (strength) but distinct: bala is the absolute strength that enables all activity, while vīrya specifically emphasizes the non-diminution — the fact that nothing leaves Brahman depleted or weaker. In the Viṣṇu Purāṇa (1.12), the six qualities are enumerated and differentiated: bala is the power to support; vīrya is the unchanging, inexhaustible nature of that support.
Devotional Significance
Recognizing the Lord's vīrya is reassuring for the devotee: the one who has accepted one's prapatti will not run out of protective energy, will not grow tired of sustaining, will not be overcome by the devotee's enemies. This grounds the rakṣiṣyati (He will protect) confidence of prapatti in something more than hope — in the Lord's own invincible nature.