Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 33
Sanskrit:
यदि वस्तत्र विश्रम्भो दानवेन्द्र जगद्गुरौ ।तर्ह्यङ्गाशु स्वशिरसि हस्तं न्यस्य प्रतीयताम् ॥ ३३ ॥
ITRANS:
yadi vas tatra viśrambhodānavendra jagad-gurautarhy aṅgāśu sva-śirasihastaṁ nyasya pratīyatām
Translation:
O best of the demons, if you have any faith in him because he is the spiritual master of the universe, then without delay put your hand on your head and see what happens.