This ahadith are from the greatest book BUKHARI SHARIF after the book of ALLAH that is Al Quraan.

Revelation

Bukhari :: Book 1 :: Volume 1 :: Hadith 1

Narrated 'Umar bin Al-Khattab:
I heard Allah's Apostle saying, "The reward of deeds depends upon the intentions and every person will get the reward according to what he has intended. So whoever emigrated for worldly benefits or for a woman to marry, his emigration was for what he emigrated for."  

Revelation

Bukhari :: Book 1 :: Volume 1 :: Hadith 2

Narrated 'Aisha:

(the mother of the faithful believers) Al-Harith bin Hisham asked Allah's Apostle "O Allah's Apostle! How is the Divine Inspiration revealed to you?" Allah's Apostle replied, "Sometimes it is (revealed) like the ringing of a bell, this form of Inspiration is the hardest of all and then this state passes ' off after I have grasped what is inspired. Sometimes the Angel comes in the form of a man and talks to me and I grasp whatever he says." 'Aisha added: Verily I saw the Prophet being inspired Divinely on a very cold day and noticed the Sweat dropping from his forehead (as the Inspiration was over).