Sahih Bukhari
Sales in which a Price is paid for Goods to be Delivered Later (As-Salam)
Volume: 003 / Book Number: 035 / Hadith Number: 453
Narrated 'Aisha:
Allah's Apostle bought some foodstuff (barley) from a Jew on credit and mortgaged his iron armor to him (the armor stands for a guarantor).