Sahih Bukhari Volume 7, Book 67, Hadith 5244

حَدَّثَنِي مَحْمُودٌ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ، أَخْبَرَنَا مَعْمَرٌ، عَنِ ابْنِ طَاوُسٍ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، قَالَ ‏"‏ قَالَ سُلَيْمَانُ بْنُ دَاوُدَ ـ عَلَيْهِمَا السَّلاَمُ ـ لأَطُوفَنَّ اللَّيْلَةَ بِمِائَةِ امْرَأَةٍ، تَلِدُ كُلُّ امْرَأَةٍ غُلاَمًا، يُقَاتِلُ فِي سَبِيلِ اللَّهِ، فَقَالَ لَهُ الْمَلَكُ قُلْ إِنْ شَاءَ اللَّهُ‏.‏ فَلَمْ يَقُلْ وَنَسِيَ، فَأَطَافَ بِهِنَّ، وَلَمْ تَلِدْ مِنْهُنَّ إِلاَّ امْرَأَةٌ نِصْفَ إِنْسَانٍ ‏"‏‏.‏ قَالَ النَّبِيُّ صلى الله عليه وسلم ‏"‏ لَوْ قَالَ إِنْ شَاءَ اللَّهُ لَمْ يَحْنَثْ، وَكَانَ أَرْجَى لِحَاجَتِهِ ‏"

Narrated By Abu Huraira : (The Prophet) Solomon son of (the Prophet) David said, "Tonight I will go round (i.e. have sexual relations with) one hundred women (my wives) everyone of whom will deliver a male child who will fight in Allah's Cause." On that an Angel said to him, "Say: 'If Allah will.' " But Solomon did not say it and forgot to say it. Then he had sexual relations with them but none of them delivered any child except one who delivered a half person. The Prophet said, "If Solomon had said: 'If Allah will,' Allah would have fulfilled his (above) desire and that saying would have made him more hopeful."