The hadith that describes the the human development in the first forty days  was narrated by  Abdullah Ibn  Mas’ud -  he may be blessed by Allah – , he said :  Allah’s Messenger ( peace and blessings be upon him ), the  truthful and  truly-inspired (trusted) , said  : Each one one of you  is collected (i.e. constituents of creation are collected together)  in his mother’s abdomen  (i.e. womb )  for  40 days , and in that it is an alaqah like that , then in that it is a mudghah like that. Then God sends an angle and order him with four words (i.e. instructions) . He is told to record  his  livelihood ( his sustenance ) , his age , his  deeds , whether he will be miserable or happy , and then the spirit is breathed into him  (i.e. the soul is acquired)…”      (This is narrated in Sahih Muslim, book of destiny ” in Arabic Kitab al-Kadar”  and also  in Sahih Al-Bukhari , beginning of creation book “in Arabic Kitab Ba’doul Khalq “ ; the words of the hadith mentioned above is that shown by Muslim narration , which the the same as that shown in  the narration of Al-Bukhari , except  that the phrase “in that” was  not mentioned )...

There are two facts in the preceding hadith:

1. The collection of constituents of creation ( In Arabic : yojmah Khalqhu ) : occurs in the first 40 days.

2. During this period , the early stages of development ( nutfah , alaqah and mudghah ) begin and end .

       According to modern embryology , it has been established that in 5th  week , the embryo acquires a characteristic C-shaped curvature, its size does not exceed 0.5 inch , its upper part is two-thirds of its total size, it acquires limb buds , and it has a tail and a primitive heart that beats regularly. The upper limbs appear during  4th  week and in  the beginning of 5th  week, they look like a paddle. However, the upper limbs begin, by the end of  5th  week, to show some regional differentiation as the hand plates develop and show finger rays . Before the 40th  day, the embryo has primitive eyes, ears, and genitalia that are functionless and do not look human. By the end of  6th week, before the 42nd day, the face is neither distinct nor looks human . 

        This above description of the conceptus development is identical to the meaning of the phrase “constituents of creation are collected together” (or in Arabic yojmah Khalqhu ) in this hadith as it describes the external curved or “C”-like appearance of embryo as well as its internal anatomy  ; where the body organs and systems are collected in their primitive forms inside this small mass.

The stages of the embryo during the first 40 days, according to the previous hadith :
1. Nutfah Stage:       In very early development,  the fusion of sperm and ovum occurs to form the zygote ( the fertilized ovum) or the nutfah amshaj . The process of implantation  in humans, begins about the 6th day after fertilization and  by the end of the first week the fertilized ovum  changes into the blastocyst and becomes superficially implanted in the endometrium . Thus , the nutfah stage is completed in around day 7 of fertilization, taking its share of the first 40 days . 

2. Alaqah Stage : After nutfah stage, cells continue to accumulate. The embryo becomes more solid as more and more cells begin to accumulate, later  its surface dent  as the neural folds develop . With the end of this stage, about 24 or 25 days of age, the embryo is hanged by the connecting stalk to the wall of the chorionic vesicle .  In this manner, the  alaqah stage takes its share of the first 40 days.

3. Mudghah Stage : This stage begins on about day 26 or 27 , and  the body masses, or somites continue to form and  gradually increase in number  on the dorsal aspect of the embryo, up to its tail region .  These somites will form the backbone of the embryo. The size of the embryo becomes like the size of  the smallest piece of meat that can be chewed . The external appearance of this small piece of meat is shapeless , but due to the denting by the somites , it  resembles a chewed substance like gum, and it does not have any human characteristics. This stage ends by the end  of 6th week  and thus the mudghah  takes its share in the first 40 days. During the 7th week, the embryo gradually acquires a human appearance as the skeleton starts to become obvious.

         Thus, the hadith indicates that the stages of nutfah, alaqah and mudghah occur during the first 40 days. A question should be asked now ,  from any source in the seventh century could prophet Mohammad , peace and blessings be upon him , take these details of embryonic development  ??   Before answering this question , one should know that during these 40 days , the embryo is very small , and the durations between the successive stages are short. The estimation of the embryo’s age before the discovery of the ovum and its association with the menstrual cycle was very difficult, and error could result in an underestimation of gestational age by up to 21 days, since conception could have occurred at any time between the menses . Moreover, the stages of nutfah, alaqah and mudghah, mentioned in the Qur’an and Sunnah , were not even recognized by scientific knowledge at that time. Thus , the logic  answer , without any doubt , this  information  is a revelation from God who is the All-knowing…