Thereafter the legs of the gigantic form separately became manifest, and the demigod named Viṣṇu [not the Personality of Godhead] entered with partial movement. This helps the living entity move to his destination.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
पादावस्य विनिर्भिन्नौ लोकेशो विष्णुराविशत् । गत्या स्वांशेन पुरुषो यया प्राप्यं प्रपद्यते
pādāvasya vinirbhinnau lokeśo viṣṇurāviśat | gatyā svāṃśena puruṣo yayā prāpyaṃ prapadyate
SB 3.6.22