Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 42
Sanskrit:
दग्ध्वा वाराणसीं सर्वां विष्णोश्चक्रं सुदर्शनम् ।भूय: पार्श्वमुपातिष्ठत् कृष्णस्याक्लिष्टकर्मण: ॥ ४२ ॥
ITRANS:
dagdhvā vārāṇasīṁ sarvāṁviṣṇoś cakraṁ sudarśanambhūyaḥ pārśvam upātiṣṭhatkṛṣṇasyākliṣṭa-karmaṇaḥ
Translation:
After burning down the entire city of Vārāṇasī, Lord Viṣṇu’s Sudarśana cakra returned to the side of Śrī Kṛṣṇa, whose actions are effortless.