The gigantic universal form of the Supreme Lord is the first incarnation and plenary portion of the Supersoul. He is the Self of an unlimited number of living entities, and in Him rests the aggregate creation, which thus flourishes.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
एष ह्यशेषसत्त्वानामात्मांशः परमात्मनः । आद्योऽवतारो यत्रासौ भूतग्रामो विभाव्यते
eṣa hyaśeṣasattvānāmātmāṃśaḥ paramātmanaḥ | ādyo'vatāro yatrāsau bhūtagrāmo vibhāvyate
SB 3.6.8