Shiva Purana
कूर्मोंगानि यथा पूर्वं प्रसार्य विनियच्छति ॥ विकारांश्च तथा ऽव्यक्तं सृष्ट्वा भूयो नियच्छति ॥ ३८ ॥
Just as the tortoise spreads its limbs first and then withdraws them, so the Avyakta creates the beings and then withdraws them.
english translation
kUrmoMgAni yathA pUrvaM prasArya viniyacchati ॥ vikArAMzca tathA 'vyaktaM sRSTvA bhUyo niyacchati ॥ 38 ॥
hk transliteration by Sanscript