āpaḥ puruṣa-vīryāḥ stha
punantīr bhūr-bhuvaḥ-suvaḥ
tā naḥ punītāmīva-ghnīḥ
spṛśatām ātmanā bhuva iti
āpaḥ - O water; puruṣa-vīryāḥ - endowed with the energy of the Supreme Personality of Godhead; stha - you are; punantīḥ - sanctifying; bhūḥ - of the planetary system known as Bhūḥ; bhuvaḥ - of the Bhuvaḥ planetary system; suvaḥ - of the Svaḥ planetary system; tāḥ - that water; naḥ - of us; punīta - purify; amīva-ghnīḥ - who destroys sin; spṛśatām - of those touching; ātmanā - by your constitutional position; bhuvaḥ - the bodies; iti - thus.
Kṛṣṇa says in Bhagavad-gītā (7.4):
bhūmir āpo ’nalo vāyuḥ
khaṁ mano buddhir eva ca
ahaṅkāra itīyaṁ me
bhinnā prakṛtir aṣṭadhā
“Earth, water, fire, air, ether, mind, intelligence and false ego — all together these eight comprise My separated material energies.”
The energy of the Lord acts throughout the creation, just as heat and light, the energies of the sun, act within the universe and make everything work. The specific rivers mentioned in the śāstras are also energies of the Supreme Personality of Godhead, and people who regularly bathe in them are purified. It can actually be seen that many people are cured of diseases simply by bathing in the Ganges. Similarly, the inhabitants of Krauñcadvīpa purify themselves by bathing in the rivers there.