Infinite Strength as Divine Quality
Bala ('strength,' 'power') is one of the six primary qualities (ṣaḍguṇas) of Brahman. It refers to the absolute power by which the Lord supports all of existence — Brahman is the ādhāra (substratum/support) of all, needing no support Himself. As the Bhagavad Gītā states: gām āviśya ca bhūtāni dhārayāmy aham ojasā — 'Entering the earth, I sustain all beings by My power.'
Bala as Foundation
The theological implication of bala: Brahman is the one being who requires no foundation other than Himself. All other beings — the earth, space, the gods, living creatures — require support; Brahman alone is self-supporting and supports all others. This self-sufficient support-power is bala in its deepest sense.
Narasiṃha as Revelation of Bala
The Narasiṃha avatāra is often cited as the most dramatic revelation of the Lord's bala: the Lord, appearing from within a pillar in a form that violated every natural category (neither man nor beast, neither inside nor outside, neither day nor night), demonstrated that His power transcends all conditions. Prahlāda's faith in the Lord's bala — 'The Lord is everywhere and can protect me from anywhere' — was vindicated.
Relationship to Vīrya
Bala and vīrya are related but distinct: bala is the positive capacity for power (the strength to sustain, to act), while vīrya is the quality of being undiminished (the strength is not depleted by action). Together they describe a Lord who can do everything and is exhausted by nothing.