Shiva Purana
उपस्थाय प्रविश्याप्सु नाभिदघ्नं प्रवेशयन् ॥ तन्मन्त्रान्प्रजपेत्प्रीत्या निश्चलात्मा समुत्सुकः ॥ ४५॥
He approached and entered the waters and inserted the navel-killer. One should chant these mantras with devotion and with a steady mind and eagerness.
english translation
upasthAya pravizyApsu nAbhidaghnaM pravezayan ॥ tanmantrAnprajapetprItyA nizcalAtmA samutsukaH ॥ 45॥
hk transliteration by Sanscript