Shiva Purana

siva.sh/siva-purana/saturda-samhita/24/63

अथ रुद्रः पिप्पलादोऽश्वत्थमूले महाप्रभुः ।। तताप सुचिरं कालं लोकानां हितकाम्यया।। ६३।।

sanskrit

Then Rudra, the great lord in the form of Pippalāda, performed a penance for a long time at the foot of the fig tree, with a desire to bestow benefit on the worlds.

english translation

atha rudraH pippalAdo'zvatthamUle mahAprabhuH || tatApa suciraM kAlaM lokAnAM hitakAmyayA|| 63||

hk transliteration by Sanscript