Skandapurana 6.3.238.p23

6.3.238.p23

22 gaṃgādiṣoḍaśanadīnāṃ patnītvena prāptaye'gnineśvaramuddiśya tapaḥkaraṇam, tena tapasā saṃtuṣṭena śaṃkareṇāgnaye varapradānam , viśalyāsaṃbhavavarṇanam. .. ... 198 2

22. Agni's performing austerity directed towards Īśvara in order to obtain the sixteen rivers, including the Gaṅgā, as wives; Śaṃkara, pleased by that austerity, granting a boon to Agni; description of the origin of the Viśalyā river. 198 2