Ja'far bin Muhammad bin 'Ali bin Al-Husain narrated from his father, that Jabir bin 'Abdullah said:
"The Messenger of Allah (ﷺ) prayed Subh as soon as he was certain the dawn had appeared." (TR)
English reference (TR): Vol. 1, Book 6, Hadith 544 (TR)
Arabic reference (TR): Book 6, Hadith 548 (TR)