Narrated Abu Huraira:Allah's Messenger (ﷺ) said, "(The Prophet) Solomon once said, 'Tonight I will sleep with ninety women, each of whom will bring forth a (would-be) cavalier who will fight in Allah's Cause." On this, his companion said to him, "Say: Allah willing!" But he did not say Allah willing. Solomon then slept with all the women, but none of them became pregnant but one woman who later delivered a halfman. By Him in Whose Hand Muhammad's soul is, if he (Solomon) had said, 'Allah willing' (all his wives would have brought forth boys) and they would have fought in Allah's Cause as cavaliers. "
حَدَّثَنَا أَبُو الْيَمَانِ، أَخْبَرَنَا شُعَيْبٌ، حَدَّثَنَا أَبُو الزِّنَادِ، عَنْ عَبْدِ الرَّحْمَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " قَالَ سُلَيْمَانُ لأَطُوفَنَّ اللَّيْلَةَ عَلَى تِسْعِينَ امْرَأَةً، كُلُّهُنَّ تَأْتِي بِفَارِسٍ يُجَاهِدُ فِي سَبِيلِ اللَّهِ. فَقَالَ لَهُ صَاحِبُهُ إِنْ شَاءَ اللَّهُ. فَلَمْ يَقُلْ إِنْ شَاءَ اللَّهُ. فَطَافَ عَلَيْهِنَّ جَمِيعًا، فَلَمْ تَحْمِلْ مِنْهُنَّ إِلاَّ امْرَأَةٌ وَاحِدَةٌ، جَاءَتْ بِشِقِّ رَجُلٍ، وَايْمُ الَّذِي نَفْسُ مُحَمَّدٍ بِيَدِهِ لَوْ قَالَ إِنْ شَاءَ اللَّهُ. لَجَاهَدُوا فِي سَبِيلِ اللَّهِ فُرْسَانًا أَجْمَعُونَ ".
Bukhari
Oaths and Vows • Hadith 18