Hadithcore
Mishkat al-Masabih, 4627

Abu Sa'id reported the Prophet (ﷺ) as saying:

“The truest vision comes a little before daybreak.” Tirmidhi and Darimi transmitted it.

وَعَنْ أَبِي سَعِيدٍ عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «أَصْدَقُ الرُّؤْيَا بِالْأَسْحَارِ» . رَوَاهُ التِّرْمِذِيّ والدارمي نِهَايَة الْجُزْء الثَّانِي

References1 variant
In-Book Reference
Book 24, Hadith 20