Śrīmad-Bhāgavatam · Text 2.6.11
Who is speaking and story frame
अव्यक्तरससिन्धूनां भूतानां निधनस्य च ।
उदरं विदितं पुंसो हृदयं मनस: पदम् ॥ ११ ॥
avyakta-rasa-sindhūnāṁ
bhūtānāṁ nidhanasya ca
udaraṁ viditaṁ puṁso
hṛdayaṁ manasaḥ padam
The impersonal feature of the Lord is the abode of great oceans, and His belly is the resting place for the materially annihilated living entities. His heart is the abode of the subtle material bodies of living beings. Thus it is known by the intelligent class of men.
Read Śrīla Prabhupāda's purport on Vedabase.io