Sahih Muslim 2645
Sahih Muslim · Book 46: The Book of Destiny · How The Human Being Is Created, In His Mother's Womb, And His Provision, Lifespan And Deeds Are Written Down, And His Misery and Happiness
Hadhaifa b. Usaid Ghifari, a Companion of Allah's Messenger (ﷺ), reported it directly from Allah's Messenger (may peace upon him). as he said:
حَدَّثَنَا عَبْدُ الْوَارِثِ بْنُ عَبْدِ الصَّمَدِ ، حَدَّثَنِي أَبِي ، حَدَّثَنَا رَبِيعَةُ بْنُ كُلْثُومٍ ، حَدَّثَنِي أَبِي كُلْثُومٌ ، عَنْ أَبِي الطُّفَيْلِ ، عَنْ حُذَيْفَةَ بْنِ أَسِيدٍ الْغِفَارِيِّ ، صَاحِبِ رَسُولِ اللَّهِ صلى الله عليه وسلم رَفَعَ الْحَدِيثَ إِلَى رَسُولِ اللَّهِ صلى الله عليه وسلم " أَنَّ مَلَكًا مُوَكَّلاً بِالرَّحِمِ إِذَا أَرَادَ اللَّهُ أَنْ يَخْلُقَ شَيْئًا بِإِذْنِ اللَّهِ لِبِضْعٍ وَأَرْبَعِينَ لَيْلَةً " . ثُمَّ ذَكَرَ نَحْوَ حَدِيثِهِمْ .
There is an angel who looks after the womb when Allah decides to create any- thing after more than forty nights are over; the rest of the hadith is the same.