Srimad-Bhagavatam: Canto 11 - Chapter 1 - Verse 4

Sanskrit:

ग्रीष्मे तप्येत पञ्चाग्नीन् वर्षास्वासारषाड्‍जले ।आकण्ठमग्न: शिशिर एवंवृत्तस्तपश्चरेत् ॥ ४ ॥

ITRANS:

grīṣme tapyeta pañcāgnīnvarṣāsv āsāra-ṣāḍ jaleākaṇtha-magnaḥ śiśiraevaṁ vṛttas tapaś caret

Translation:

Thus engaged as a vānaprastha, one should execute penance during the hottest summer days by subjecting oneself to burning fires on four sides and the blazing sun overhead; during the rainy season one should remain outside, subjecting oneself to torrents of rain; and in the freezing winter one should remain submerged in water up to one’s neck.

Purport:

One who engages in sense gratification must perform severe penances at the end of life to counteract his sinful, hedonistic activities. A devotee of the Lord, however, naturally develops Kṛṣṇa consciousness and need not subject himself to such radical penances. As stated in the Pañcarātra: “If one is worshiping the Lord properly, what is the use of severe penances? And if one is not properly worshiping the Lord, what is the use of severe penances? If Śrī Kṛṣṇa is realized within and without everything that exists, what is the use of severe penances? And if Śrī Kṛṣṇa is not seen within and without everything, then what is the use of severe penances?”