Mishkat al-Masabih 4623
A‘isha told that God’s messenger was questioned about Waraqa and Khadija said to him, “He believed on you, but died before you appeared as a prophet.” God’s messenger then said:
“I was shown him in a dream wearing white clothes, and if he had been one of the inhabitants of hell he would have been wearing different clothing.” 

Ahmad and Tirmidhi transmitted it.
وَعَنْ عَائِشَةَ رَضِيَ اللَّهُ عَنْهَا قَالَتْ سُئِلَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ عَن وَرَقَةَ. فَقَالَتْ لَهُ خَدِيجَةُ: إِنَّهُ كَانَ قَدْ صَدَّقَكَ وَلَكِنْ مَاتَ قَبْلَ أَنْ تَظْهَرَ. فَقَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «أُرِيتُهُ فِي الْمَنَامِ وَعَلَيْهِ ثِيَابٌ بِيضٌ وَلَوْ كَانَ مِنْ أَهْلِ النَّارِ لَكَانَ عَلَيْهِ لِبَاسٌ غَيْرُ ذَلِك» . رَوَاهُ أَحْمد وَالتِّرْمِذِيّ