بُلُوغُ الْمَرَامِ
Bulugh al-Maram 168
The Book of Prayer
وَعَنْ اِبْنِ عُمَرَ رَضِيَ اَللَّهُ عَنْهُمَا; عَنْ اَلنَّبِيِّ - صلى الله عليه وسلم -قَالَ: { اَلشَّفَقُ اَلْحُمْرَةُ } رَوَاهُ اَلدَّارَقُطْنِيُّ وَصَحَّحَ اِبْنُ خُزَيْمَةَ وَغَيْرُهُ وَقْفَهُ [1] .
Narrated Ibn 'Umar (RA): The Prophet (ﷺ) said: "The twilight is the redness." [Reported by ad-Daraqutni. Ibn Khuzaimah graded it Sahih (authentic) and others graded it Mawquf (a saying of a Companion)].
Sunnah.com reference: Book 2, Hadith 20