Sahih Muslim Book - 46, Hadith - 6730

حَدَّثَنِي أَبُو كَامِلٍ فُضَيْلُ بْنُ حُسَيْنٍ الْجَحْدَرِيُّ ، حَدَّثَنَا حَمَّادُ بْنُ زَيْدٍ ، حَدَّثَنَا عُبَيْدُ اللهِ بْنُ أَبِي بَكْرٍ ، عَنْ أَنَسِ بْنِ مَالِكٍ ، وَرَفَعَ الْحَدِيثَ ، أَنَّهُ قَالَ: إِنَّ اللَّهَ عَزَّ وَجَلَّ قَدْ وَكَّلَ بِالرَّحِمِ مَلَكًا ، فَيَقُولُ : أَيْ رَبِّ نُطْفَةٌ ، أَيْ رَبِّ عَلَقَةٌ ، أَيْ رَبِّ مُضْغَةٌ ، فَإِذَا أَرَادَ اللَّهُ أَنْ يَقْضِيَ خَلْقًا قَالَ: قَالَ الْمَلَكُ: أَيْ رَبِّ ذَكَرٌ ، أَوْ أُنْثَى ؟ شَقِيٌّ ، أَوْ سَعِيدٌ ؟ فَمَا الرِّزْقُ ؟ فَمَا الأَجَلُ ؟ فَيُكْتَبُ كَذَلِكَ فِي بَطْنِ أُمِّهِ.

It was narrated from Anas bin. Malik that the Prophet (s.a.w) said: "Allah, Glorified and Exalted is He, has appointed an angel over the womb, and he says: 'O Lord, a Nutfah (sperm drop); O lord, an 'Alaqah; O Lord, a Mudghah.' Then when Allah wants to decree the (final stage of) his creation, the angel says: 'O Lord, male or female? Miserable or happy? What is his provision? What is his lifespan?' And that is written in the womb of his mother."