Sahih Muslim Book 31, Hadith Number 5972.

Chapter : The merits of Hadrat Khadija, mother of the faithful (Allah be pleased with her).

‘Aisha 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.