The almighty Personality of Godhead, Śrī Kṛṣṇa, having observed that a great danger was befalling His unalloyed devotees, who were fully surrendered souls, at once took up His Sudarśana disc to protect them.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
व्यसनं वीक्ष्य तत्तेषामनन्यविषयात्मनाम् । सुदर्शनेन स्वास्त्रेण स्वानां रक्षां व्यधाद्विभुः
vyasanaṃ vīkṣya tatteṣāmananyaviṣayātmanām | sudarśanena svāstreṇa svānāṃ rakṣāṃ vyadhādvibhuḥ
SB 1.8.13