Sayyiduna al-Harith bin Hisham (may Allah be pleased with him) said: I asked the Messenger of Allah (peace and blessings be upon him): How does the revelation come to you? He (peace and blessings be upon him) said: "It comes to me like the ringing of a bell; and sometimes he comes in the form of a man and speaks to me, and this is easier on me; then that state leaves me, and I have retained everything."
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 3331