Sahih Muslim 4288
صحيح مسلم#4288SahihAbu Huraira reported that Sulaiman b. Dawud said:I will certainly have intercourse with seventy wives during the night, and every wife amongst them will give birth to a child, who will fight in the cause of Allah. It was said to him: Say:" Insha' Allah" (God willing), but he did not say so and forgot it. He went round them but none of them give birth to a child except one woman and that too was an incomplete person. Upon this Allah's Messenger (ﷺ) said: If he had said" Insha' Allah." he would not have failed, and his desire must have been fulfilled
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 27:35