Shiva Purana

siva.sh/siva-purana/uma-samhita/22/16

संवृतः प्रविशेद्योनिं कर्मभिस्स्वैर्नियोजितः ।। तच्छुक्ररक्तमेकस्थमेकाहात्कलिलं भवेत् ।। १६ ।।

sanskrit

He enters the womb enveloped and engaged in his own actions. That blood of Venus in one place will become Kalila in one day.

english translation

saMvRtaH pravizedyoniM karmabhissvairniyojitaH || tacchukraraktamekasthamekAhAtkalilaM bhavet || 16 ||

hk transliteration by Sanscript