(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 ﷺ said, "If Solomon had said: 'If Allah will,' Allah would have fulfilled his (above) desire and that saying would have made him more hopeful."  

لَهُ الْمَلَكُ قُلْ إِنْ شَاءَ اللَّهُ فَلَمْ يَقُلْ وَنَسِيَ فَأَطَافَ بِهِنَّ وَلَمْ تَلِدْ مِنْهُنَّ إِلاَّ امْرَأَةٌ نِصْفَ إِنْسَانٍ قَالَ النَّبِيُّ ﷺ لَوْ قَالَ إِنْ شَاءَ اللَّهُ لَمْ يَحْنَثْ وَكَانَ أَرْجَى لِحَاجَتِهِ  

The Prophet ﷺ said, "Solomon (the son of) David said, 'Tonight I will sleep with seventy ladies each of whom will conceive a child who will be a knight fighting for "Allah's Cause.' His companion said, 'If Allah will.' But Solomon did not say so; therefore none of those women got pregnant except one who gave birth to a half child." The Prophet ﷺ further said, "If the Prophet ﷺ Solomon had said it (i.e. 'If Allah will') he would have begotten children who would have fought in Allah's Cause." Shuaib and Ibn Abi Az-Zinad said, "Ninety (women) is more correct (than seventy).  

عَنِ النَّبِيِّ ﷺ قَالَ قَالَ سُلَيْمَانُ بْنُ دَاوُدَ لأَطُوفَنَّ اللَّيْلَةَ عَلَى سَبْعِينَ امْرَأَةً تَحْمِلُ كُلُّ امْرَأَةٍ فَارِسًا يُجَاهِدُ فِي سَبِيلِ اللَّهِ فَقَالَ لَهُ صَاحِبُهُ إِنْ شَاءَ اللَّهُ فَلَمْ يَقُلْ وَلَمْ تَحْمِلْ شَيْئًا إِلاَّ وَاحِدًا سَاقِطًا إِحْدَى شِقَّيْهِ فَقَالَ النَّبِيُّ ﷺ لَوْ قَالَهَا لَجَاهَدُوا فِي سَبِيلِ اللَّهِ قَالَ شُعَيْبٌ وَابْنُ أَبِي الزِّنَادِ تِسْعِينَ وَهْوَ أَصَحُّ