Mishkat al-Masabih 27 Fitan كتاب الفتن 117

وَعَنْهُ أَنَّ ابْنَ صَيَّادٍ سَأَلَ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ عَنْ تُرْبَةِ الْجَنَّةِ. فَقَالَ: «در مَكَّة يبضاء ومسك خَالص» . رَوَاهُ مُسلم

He told that Ibn Sayyad asked the Prophet about the soil of paradise and that he replied it was a white, sifted flour and pure musk. Muslim transmitted it.