صحيح مسلم

Abu Huraira reported Allah's Messenger (ﷺ) as saying that Sulaiman b. Dawud (once) said: I will go round in the night to my ninety wives, and every one of them will give birth to a child (who will grow up) as a horseman and fight in the cause of Allah His companions said to him: Say" Insha' Allah." but he did not say Inshii' Allah. He went round all of them but none of them became pregnant but one, and she gave birth to a premature child. And by Him in Whose hand is the life of Muhammad, if he had said, Insha' Allah (his wives would have given birth to the children who would all have grown up into horsemen and fought in the way of Allah).