The Prophet ﷺ said, "Bilal calls the adhan at night to wake those of you who are sleeping and to bring back those of you who are standing in prayer. It is not meant to indicate this," meaning the break of dawn.
أخبرنا إسحق بن إبراهيم قال أنبأنا المعتمر بن سليمان عن أبيه عن أبي عثمان
عن النبي ﷺ قال إن بلالا يؤذن بليل ليوقظ نائمكم وليرجع قائمكم وليس أن يقول هكذا يعني في الصبح
Muslim narrated it in the Book of Fasting, Chapter on the Explanation that Entering the Fast Occurs with the Rising of Fajr, hadith 40/1093, from Ishaq bin Ibrahim, and Bukhari narrated it in the Book of Adhan, Chapter on the Adhan before Fajr, hadith 621, from the hadith of Sulayman Taymi with the same wording. It is also in Kubra, hadith 1605.