Sahih Bukhari Volume 4, Book 59, Hadith 3216

حَدَّثَنَا فَرْوَةُ، حَدَّثَنَا عَلِيُّ بْنُ مُسْهِرٍ، عَنْ هِشَامِ بْنِ عُرْوَةَ، عَنْ أَبِيهِ، عَنْ عَائِشَةَ ـ رضى الله عنها ـ أَنَّ الْحَارِثَ بْنَ هِشَامٍ، سَأَلَ النَّبِيَّ صلى الله عليه وسلم كَيْفَ يَأْتِيكَ الْوَحْىُ قَالَ ‏"‏ كُلُّ ذَاكَ يَأْتِي الْمَلَكُ أَحْيَانًا فِي مِثْلِ صَلْصَلَةِ الْجَرَسِ، فَيَفْصِمُ عَنِّي وَقَدْ وَعَيْتُ مَا قَالَ، وَهْوَ أَشَدُّهُ عَلَىَّ، وَيَتَمَثَّلُ لِي الْمَلَكُ أَحْيَانًا رَجُلاً، فَيُكَلِّمُنِي فَأَعِي مَا يَقُولُ ‏"‏‏

Narrated By 'Aisha : Al Harith bin Hisham asked the Prophet, "How does the divine inspiration come to you?" He replied, "In all these ways: The Angel sometimes comes to me with a voice which resembles the sound of a ringing bell, and when this state abandons me, I remember what the Angel has said, and this type of Divine Inspiration is the hardest on me; and sometimes the Angel comes to me in the shape of a man and talks to me, and I understand and remember what he says."