Because the Supreme Personality of Godhead was within her womb, Devakī illuminated the entire atmosphere in the place where she was confined. Seeing her jubilant, pure and smiling, Kaṁsa thought, “The Supreme Personality of Godhead, Viṣṇu, who is now within her, will kill me. Devakī has never before looked so brilliant and jubilant.”
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
तां वीक्ष्य कंसः प्रभयाजितान्तरां विरोचयन्तीं भवनं शुचिस्मिताम् । आहैष मे प्राणहरो हरिर्गुहां ध्रुवं श्रितो यन्न पुरेयमीदृशी
tāṃ vīkṣya kaṃsaḥ prabhayājitāntarāṃ virocayantīṃ bhavanaṃ śucismitām | āhaiṣa me prāṇaharo harirguhāṃ dhruvaṃ śrito yanna pureyamīdṛśī
SB 10.2.20