Revākhaṇḍa ascribed to the Vāyupurāṇa (RKV) 118.18

118.18

ārdravāsāstu hemante cacāra vipulaṃ tapaḥ /
evaṃ tu tapatastasya indrasya viditātmanaḥ //

and clad in wet garments during the winter, he performed severe asceticism. / While Indra, whose self was disciplined, was thus performing asceticism,