Srimad-Bhagavatam: Canto 4 - Chapter 1 - Verse 30
Sanskrit:
न वध्यो भवतामिन्द्रो यद्यज्ञो भगवत्तनु: ।यं जिघांसथ यज्ञेन यस्येष्टास्तनव: सुरा: ॥ ३० ॥
ITRANS:
na vadhyo bhavatām indroyad yajño bhagavat-tanuḥyaṁ jighāṁsatha yajñenayasyeṣṭās tanavaḥ surāḥ
Translation:
Lord Brahmā addressed them thus: My dear sacrificial performers, you cannot kill Indra, the King of heaven. It is not your duty. You should know that Indra is as good as the Supreme Personality of Godhead. Indeed, he is one of the most powerful assistants of the Personality of Godhead. You are trying to satisfy all the demigods by the performance of this yajña, but you should know that all these demigods are but parts and parcels of Indra, the King of heaven. How, then, can you kill him in this great sacrifice?