بُلُوغُ الْمَرَامِ
Bulugh al-Maram 160
The Book of Prayer
وَعَنْ رَافِعِ بْنِ خَدِيجٍ - رضى الله عنه - قَالَ: قَالَ رَسُولُ اَللَّهِ - صلى الله عليه وسلم -{ أَصْبِحُوا بِالصُّبْحِ فَإِنَّهُ أَعْظَمُ لِأُجُورِكُمْ } رَوَاهُ اَلْخَمْسَةُ, وَصَحَّحَهُ اَلتِّرْمِذِيُّ, وَابْنُ حِبَّانَ [1] .
Narrated Rafi' bin Khadij (RA): Allah's Messenger (ﷺ) said: "Offer the morning prayer at dawn, for it is greater for your rewards." [Reported by al-Khamsah. at-Tirmidhi and Ibn Hibban graded it Sahih (authentic)].
Sunnah.com reference: Book 2, Hadith 10