The Messenger of Allah ﷺ said, "When Ibn Umm Maktum calls the adhan, eat and drink. But when Bilal calls the adhan, do not eat or drink."Sometimes one of us would still have part of her pre-dawn meal left, so 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 الواحدة منا ليبقى عليها الشيء من سحورها فتقول لبلال: أمهل حتى أفرغ من سحوري.
Nasai (640), Ibn Khuzayma (404), Ibn Hibban (3474), and Ahmad (27440) all narrated it through Hushaym, who said, Mansur bin Zazan told us, from Khubayb bin Abdul-Rahman, from his paternal aunt Anisah bint Habib, and he related it. Its chain of transmission is sahih. See the book on adhan.As for what was narrated from Zayd bin Thabit, that the Messenger of Allah ﷺ said, "Ibn Umm Maktum gives the adhan while it is still night, so eat and drink until Bilal gives the adhan," this is daif, since it contains Muhammad bin Umar Waqidi, who is very daif. Bayhaqi narrated it through his route (1/382).