The subtle subject matter of creation, on which the Lord’s attention was fixed, was agitated by the material mode of passion, and thus the subtle form of creation pierced through His abdomen.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
तस्यार्थसूक्ष्माभिनिविष्टदृष्टे- रन्तर्गतोऽर्थो रजसा तनीयान् । गुणेन कालानुगतेन विद्धः सूष्यंस्तदाभिद्यत नाभिदेशात्
tasyārthasūkṣmābhiniviṣṭadṛṣṭe- rantargato'rtho rajasā tanīyān | guṇena kālānugatena viddhaḥ sūṣyaṃstadābhidyata nābhideśāt
SB 3.8.13