Sahih Muslim Book - 27, Hadith - 4288

وَحَدَّثَنَا عَبْدُ بْنُ حُمَيْدٍ أَخْبَرَنَا عَبْدُ الرَّزَّاقِ بْنُ هَمَّامٍ أَخْبَرَنَا مَعْمَرٌ عَنِ ابْنِ طَاوُسٍ عَنْ أَبِيهِ عَنْ أَبِى هُرَيْرَةَ قَالَ قَالَ سُلَيْمَانُ بْنُ دَاوُدَ لأُطِيفَنَّ اللَّيْلَةَ عَلَى سَبْعِينَ امْرَأَةً تَلِدُ كُلُّ امْرَأَةٍ مِنْهُنَّ غُلاَمًا يُقَاتِلُ فِى سَبِيلِ اللَّهِ. فَقِيلَ لَهُ قُلْ إِنْ شَاءَ اللَّهُ. فَلَمْ يَقُلْ. فَأَطَافَ بِهِنَّ فَلَمْ تَلِدْ مِنْهُنَّ إِلاَّ امْرَأَةٌ وَاحِدَةٌ نِصْفَ إِنْسَانٍ. قَالَ فَقَالَ رَسُولُ اللَّهِ -صلى الله عليه وسلم- « لَوْ قَالَ إِنْ شَاءَ اللَّهُ. لَمْ يَحْنَثْ وَكَانَ دَرَكًا لِحَاجَتِهِ ».

It was narrated that Abu Hurairah said: "Sulaiman bin Dawud said: 'Tonight I will go around to seventy women and each of them will give birth to a boy who will fight in the cause of Allah.' It was said to him: 'Say: "If Allah wills,"' but he did not say it. He went around to them, but none of them gave birth except one woman, who gave birth to an malformed child.'' The Messenger of Allah (s.a.w) said: "If he had said 'If Allah wills,' he would not have broken his oath, and that could have been a means of fulfilling his wish."