Sahih Bukhari
Sales in which a Price is paid for Goods to be Delivered Later (As-Salam)
Volume: 003 / Book Number: 035 / Hadith Number: 460
Narrated Aisha:
I said, "O Allah's Apostle! I have two neighbors and would like to know to which of them I should give presents." He replied, "To the one whose door is nearer to you."