He reported God's messenger as telling that Solomon said, "I shall to-night visit ninety women (a version has a hundred) all of whom will give birth to a horseman who will fight in God's path." The angel told him to say, "If God will," but he forgot and did not say it. He visited them and none of them bore a child except one of them who gave birth to half a man. He added, "By Him in whose hand Muhammad's soul is, if he had said, `If God will,' they would all have striven as horsemen in God's path." (Bukhari and Muslim.)
Source: sunnah.com
Other translations
Arabic
وَعَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: " قَالَ سُلَيْمَانُ: لَأَطُوفَنَّ اللَّيْلَةَ عَلَى تِسْعِينَ امْرَأَةٍ - وَفِي رِوَايَةٍ: بِمِائَةِ امْرَأَةٍ - كُلُّهُنَّ تَأْتِي بِفَارِسٍ يُجَاهِدُ فِي سَبِيلِ اللَّهِ. فَقَالَ لَهُ الْمَلَكُ: قُلْ إِنْ شَاءَ اللَّهُ. فَلَمْ يَقُلْ وَنَسِيَ فَطَافَ عَلَيْهِنَّ فَلَمْ تحملْ منهنَّ إِلا امرأةٌ واحدةٌ جاءتْ بشقِّ رَجُلٍ وَأَيْمُ الَّذِي نَفْسُ مُحَمَّدٍ بِيَدِهِ لَوْ قَالَ: إِنْ شَاءَ اللَّهُ لَجَاهَدُوا فِي سَبِيلِ الله فُرْسَانًا أجمعونَ ". مُتَّفق عَلَيْهِ
sunnah.com