Srimad-Bhagavatam: Canto 6 - Chapter 1 - Verse 58
Sanskrit:
एवं तस्या व्रतस्थाया व्रतच्छिद्रं हरिर्नृप ।प्रेप्सु: पर्यचरज्जिह्मो मृगहेव मृगाकृति: ॥ ५८ ॥
ITRANS:
evaṁ tasyā vrata-sthāyāvrata-cchidraṁ harir nṛpaprepsuḥ paryacaraj jihmomṛga-heva mṛgākṛtiḥ
Translation:
O King Parīkṣit, as the hunter of a deer becomes like a deer by covering his body with deerskin and serving the deer, so Indra, although at heart the enemy of the sons of Diti, became outwardly friendly and served Diti in a faithful way. Indra’s purpose was to cheat Diti as soon as he could find some fault in the way she discharged the vows of the ritualistic ceremony. However, he wanted to be undetected, and therefore he served her very carefully.