Śrīmad-Bhāgavatam · Text 11.18.4
Who is speaking and story frame
ग्रीष्मे तप्येत पञ्चाग्नीन् वर्षास्वासारषाड्जले ।
आकण्ठमग्न: शिशिर एवंवृत्तस्तपश्चरेत् ॥ ४ ॥
grīṣme tapyeta pañcāgnīn
varṣāsv āsāra-ṣāḍ jale
ākaṇtha-magnaḥ śiśira
evaṁ vṛttas tapaś caret
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.
Read the purport on Vedabase.ioFrom Canto 10, chapter 14 onward, the translation and purports were completed by Śrīla Prabhupāda's disciples after his departure, and published by the Bhaktivedanta Book Trust.