Sulayman Taymi reported,

With this chain of narration. Mutamir's hadith ends at his words, "to wake your sleeper and to bring back your one praying."Ishaq said that Jareer reported in his version, "It is not that he says like this, but rather he says like this," meaning that the true dawn is the one that spreads horizontally, not the one that extends vertically.

Muslim 2543

Sahih

و حدثنا أبو بكر بن أبي شيبة حدثنا معتمر بن سليمان ح و حدثنا إسحق بن إبراهيم أخبرنا جرير والمعتمر بن سليمان كلاهما

عن سليمان التيمي

بهذا الإسناد وانتهى حديث المعتمر عند قوله ينبه نائمكم ويرجع قائمكم و قال إسحق قال جرير في حديثه وليس أن يقول هكذا ولكن يقول هكذا يعني الفجر هو المعترض وليس بالمستطيل

مسلم 2543صحيح
Contents
Reference
Commentary
Ayat
Collection
Sahih Muslim
Book
Fasting
Chapter
Clarification that entering into fasting occurs at the rising of Fajr, and that one may eat and otherwise until Fajr rises, and clarification of the description of Fajr to which rulings are attached regarding entering into fasting, the beginning of the time for the morning prayer, and other matters
Numbering
Darussalam 2543
Muslim 2543