The Messenger of Allah ﷺ said, "When Ibn Umm Maktum makes the call to prayer, eat and drink, and when Bilal makes the call to prayer, do not eat or drink."If one of our women still had part of her predawn meal left, she would say to Bilal, "Wait until I finish my suhur."
قال رسول الله ﷺ: إذا أذن ابن أم مكتوم فكلوا واشربوا، وإذا أذن بلال فلا تأكلوا ولا تشربوا فإن كانت المرأة منا ليبقى عليها شيء من سحورها فتقول لبلال: أمهل حتى أفرغ من سحوري.
Nasai (640) narrated it, he said, Yaqub bin Ibrahim informed us, from Hushaym, who said, Mansur, meaning Ibn Zazan, informed us, from Khubayb bin Abdul-Rahman, from his paternal aunt Unaysa bint Habib, and he mentioned it. Ahmad (27440) also narrated it from Hushaym through the same chain, and mentioned Unaysa's statement. Its chain of transmission is sahih, and Ibn Khuzayma also graded it sahih, narrating it (404) from Abu Hashim Ziyad bin Ayub, from Hushaym through the same chain, similarly, except that he noted a defect in it, saying, "This report has been transmitted with variation regarding Khubayb bin Abdul-Rahman. Shubah narrated it from him, from his paternal aunt Unaysa, and said, 'Ibn Umm Maktum, or Bilal, calls out at night.'" Then he narrated it through the route of Muhammad bin Jafar, from Shubah, from Khubayb, in the same manner, and likewise Ahmad (27439) also narrated it from Affan, from Shubah, through the same chain.Then Ibn Khuzayma said, "So Unaysa's report has been disputed regarding this particular wording, but Darawardi narrated from Hisham bin Urwa, from his father, from Ayesha, something matching the meaning of Mansur bin Zazan's report on this wording." End of quote.I say, Unaysa's report is sahih, and Shubah's uncertainty over whether it was Ibn Umm Maktum or Bilal does not remove the certainty in Mansur bin Zazan's hadith, for he is a trustworthy and firmly reliable narrator. It is corroborated by Ayesha's hadith mentioned earlier, and the same can be said about it as is said about Ayesha's hadith.