Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 22
Sanskrit:
तच्छ्रुत्वा भगवान् रुद्रो दुर्मना इव भारत ।ॐ इति प्रहसंस्तस्मै ददेऽहेरमृतं यथा ॥ २२ ॥
ITRANS:
tac chrutvā bhagavān rudrodurmanā iva bhārataom iti prahasaṁs tasmaidade ’her amṛtaṁ yathā
Translation:
Upon hearing this, Lord Rudra seemed somewhat disturbed. Nonetheless, O descendant of Bharata, he vibrated om to signify his assent, granting Vṛka the benediction with an ironic smile, as if giving milk to a poisonous snake.