Sahih Muslim
The Book Pertaining to the Merits of the Companions (Allah Be Pleased With Them) of the Holy Prophet (May Peace Be Upon Him) (Kitab Al-Fadail Al-Sahabah)
Book Number: 031 / Hadith Number: 5972
'A'isha reported: Never did I feel jealous of the wives of Allah's Apostle (may peace be upon him) but in case of Khadija, although I did no, (have the privilege to) see her. She further added that whenever Allah's Messenger (may peace be upon him) slaughtered a sheep, he said: Send it to the companions of Khadija I annoyed him one day and said: (It is) Khadija only who always prevails upon your mind. Thereupon Allah's Messenger (may peace be upon him) said: Her love had been nurtured in my heart by Allah Himself.