The Lord of supreme mysticism, Śrī Kṛṣṇa, resides within everyone’s heart as the Paramātmā. As such, just to protect the progeny of the Kuru dynasty, He covered the embryo of Uttarā by His personal energy.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
अन्तःस्थः सर्वभूतानामात्मा योगेश्वरो हरिः । स्वमाययाऽऽवृणोद्गर्भं वैराट्याः कुरुतन्तवे
antaḥsthaḥ sarvabhūtānāmātmā yogeśvaro hariḥ | svamāyayā''vṛṇodgarbhaṃ vairāṭyāḥ kurutantave
SB 1.8.14