It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Fajr (dawn) is of two kinds: one in which eating becomes forbidden and the prayer becomes permissible, and the other in which eating is permissible and the prayer is not permissible."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2152
Hadith Gradingمحدثین:صحيح لغيره
Hadith Takhrij«صحيح لغيره۔ مضٰي تخريجه في الحديث 1767»
It is narrated from Sayyiduna Anas bin Malik (may Allah be pleased with him) that Sayyiduna Abu Musa al-Ash'ari (may Allah be pleased with him) led them in the Fajr prayer while it was still night (before its time), then he led it again, and this happened three times.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2153