It is He Who has created you from a single person, and (then) He has created from him his wife, in order that he might enjoy the pleasure of living with her. When he covered [had sexual relation with] her, she became pregnant and she carried it about (lightly). Then when it became heavy, they both invoked Allah, their Lord (saying): "If You give us a Salih (good in every aspect) child, we shall indeed be among the grateful. (189)But when He gave them a Salih child, they ascribed partners to Him (Allah) in that which He has given to them. High be Allah, Exalted above all that they ascribe as partners to Him (190)

Allah states that He has created all mankind from Adam, peace be upon him, and from Adam, He created his wife, Hawwa' and from them, people started to spread. Allah said in another Ayah,

يَا أَيُّهَا النَّاسُ إِنَّا خَلَقْنَاكُم مِّن ذَكَرٍ وَأُنثَىٰ وَجَعَلْنَاكُمْ شُعُوبًا وَقَبَائِلَ لِتَعَارَفُوا إِنَّ أَكْرَمَكُمْ عِندَ اللَّهِ أَتْقَاكُمْ

(O mankind! We have created you from a male and a female, and made you into nations and tribes, that you may know one another. Verily, the most honorable of you with Allah is that (believer) who has Taqwa)[49:13], and,

يَا أَيُّهَا النَّاسُ اتَّقُوا رَبَّكُمُ الَّذِي خَلَقَكُم مِّن نَّفْسٍ وَاحِدَةٍ وَخَلَقَ مِنْهَا زَوْجَهَا

(O mankind! Have Taqwa of your Lord, Who created you from a single person, and from him He created his wife.)[4:1]

In this honorable Ayah, Allah said;

وَجَعَلَ مِنْهَا زَوْجَهَا لِيَسْكُنَ إِلَيْهَا

(And (then) He has created from him his wife, in order that he might enjoy the pleasure of living with her.) so that he is intimate and compassionate with her. Allah said in another Ayah,

وَمِنْ آيَاتِهِ أَنْ خَلَقَ لَكُم مِّنْ أَنفُسِكُمْ أَزْوَاجًا لِّتَسْكُنُوا إِلَيْهَا وَجَعَلَ بَيْنَكُم مَّوَدَّةً وَرَحْمَةً

(And among His Signs is this, that He created for you wives (spouses) from among yourselves, that you may find repose in them, and He has put between you affection and mercy.)[30:21]

Indeed, there is no intimacy between two souls like that between the spouses. This is why Allah mentioned that the sorcerer might be able with his trick to separate between a man and his wife [thus indicating the difficulty of separating them in normal circumstances]. Allah said next,

فَلَمَّا تَغَشَّاهَا 

(When he covered her) meaning had sexual intercourses with her.

حَمَلَتْ حَمْلًا خَفِيفًا

(she became pregnant and she carried it about lightly) in reference to the first stage of pregnancy when the woman does not feel pain, for at that time, the fetus will be just a Nutfah (the mixture of the male and female discharge), then becomes an 'Alaqah (a piece of thick coagulated blood) and then a Mudghah (a small lump of flesh). Allah said next,

فَمَرَّتْ بِهِ

(and she carried it about), she continued the pregnancy, according to Mujahid. It was reported that Al-Hasan, Ibrahim An-Nakha'i and As-Suddi said similarly. Maymun bin Mahran reported that his father said, "She found the pregnancy unnoticeable." Ayyub said, "I asked Al-Hasan about the Ayah,

فَمَرَّتْ بِهِ

(and she carried it about) and he said, 'Had you been an Arab, you would know what it means! It means that she continued the pregnancy [through its various stages].'" Qatadah said,

فَمَرَّتْ بِهِ

(and she carried it about (lightly).), means, it became clear that she was pregnant. Ibn Jarir commented, "This Ayah means that the liquid remained, whether she stood up or sat down." Al-'Awfi recorded that Ibn 'Abbas said, "The semen remained in, but she was unsure if she became pregnant or not,

فَلَمَّا أَثْقَلَت

(Then when it became heavy), she became heavier with the fetus", As-Suddi said, "The fetus grew in her womb."

دَّعَوَا اللَّهَ رَبَّهُمَا لَئِنْ آتَيْتَنَا صَالِحًا

(they both invoked Allah, their Lord (saying): "If You give us a Salih child,) if he is born human in every respect. Ad-Dahhak said that Ibn 'Abbas commented, "They feared that their child might be born in the shape of an animal!" while Abu Al-Bakhtri and Abu Malik commented, "They feared that their newborn might not be human." Al-Hasan Al-Basri also commented, "If You (Allah) give us a boy."

لَّنَكُونَنَّ مِنَ الشَّاكِرِينَ - فَلَمَّا آتَاهُمَا صَالِحًا جَعَلَا لَهُ شُرَكَاءَ فِيمَا آتَاهُمَا فَتَعَالَى اللَّهُ عَمَّا يُشْرِكُونَ

(we shall indeed be among the grateful. But when He gave them a Salih child, they ascribed partners to Him (Allah) in that which He has given to them. High be Allah, Exalted above all that they ascribe as partners to Him.)[7:189-190]

Ibn Jarir recorded that Al-Hasan commented on this part of the Ayah,

جَعَلَا لَهُ شُرَكَاءَ فِيمَا آتَاهُمَا

(they ascribed partners to Him (Allah) in that which He has given to them)

"This occurred by followers of some religion, not from Adam [or Hawwa']."

Al-Hasan also said, "This Ayah refers to those among the offspring of Adam who fell into Shirk,

جَعَلَا لَهُ شُرَكَاءَ فِيمَا آتَاهُمَا

(they ascribed partners to Him (Allah) in that which He has given to them.)"

Qatadah said, "Al-Hasan used to say that it refers to the Jews and Christians. Allah gave them children, and they turned them into Jews and Christians."

The explanations from Al-Hasan have authentic chains of narration leading to him, and certainly, it is one of the best interpretations. This Ayah should therefore be understood this way, for it is apparent that it does not refer to Adam and Hawa', but about the idolators among their offspring. Allah mentioned the person first [Adam and Hawwa'] and then continued to mention the species [mankind, many of whom committed Shirk]. There are similar cases in the Qur'an. For cases, Allah said

وَلَقَدْ زَيَّنَّا السَّمَاءَ الدُّنْيَا بِمَصَابِيحَ

(And indeed We have adorned the nearest heaven with lamps)[67:5]

It is well-known that the stars that were made as lamps in the sky are not the same as the shooting missiles that are thrown at the devils [mentioned later in the Ayah]. There are similar instances in the Qur'an. Allah knows best.