Srimad-Bhagavatam: Canto 6 - Chapter 1 - Verse 27
Sanskrit:
श्रीनारद उवाचएतां मन्त्रोपनिषदं प्रतीच्छ प्रयतो मम ।यां धारयन् सप्तरात्राद् द्रष्टा सङ्कर्षणं विभुम् ॥ २७ ॥
ITRANS:
śrī-nārada uvācaetāṁ mantropaniṣadaṁpratīccha prayato mamayāṁ dhārayan sapta-rātrāddraṣṭā saṅkarṣaṇaṁ vibhum
Translation:
The great sage Nārada continued: My dear King, attentively receive from me a mantra, which is most auspicious. After accepting it from me, in seven nights you will be able to see the Lord face to face.