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).
Sahih al-Bukhari Book 60, Hadith 96