It was narrated from Mahmud bin Labid, from some men among his people who were of the Ansar, that the Messenger of Allah (ﷺ) said:
"The more you delay Fajr, the greater the reward." (JA)
English reference (JA): Vol. 1, Book 6, Hadith 550 (JA)
Arabic reference (JA): Book 6, Hadith 554 (JA)