The works of Ādi Śaṅkarācārya

Viṣṇusahasranāmastotram

Verse 147

त्वं स्वपापपरिभ्रष्टः क्षीणपुण्यो महीपते ।दश वर्षसहस्राणि सर्परूपधरो महीम् ॥

In plain words

You have fallen, and by your own sin; your merit is spent, O king of the earth. For ten thousand years you will wear a serpent's body and travel that same earth.

Close to the Sanskrit

You, fallen away through your own sin, your merit exhausted, O lord of the earth — for ten thousand years, bearing the form of a serpent, [you shall roam] the earth.