Tafsir of Nuh 71:14

While He has created you (in) Atwar (stages). It has been said that this means from a drop of sperm, then from a hanging clot, then from a lump of flesh. Ibn `Abbas, `Ikrimah, Qatadah, Yahya bin Rafi`, As-Suddi and Ibn Zayd, all said this. Concerning Allah's statement,

ألم تروا كيف خلق الله سبع سماوات طباقا