Al-Kāfi, vol. 4, no. 734

6. A number of our people have narrated from Ahmad ibn Muhammad from ibn Faddal from ‘Abd Allah ibn Sinan who has said the following: “Abu ‘Abd Allah (a.s.), has said that when Ibrahim and Isma‘il were commanded to build the House, and when it was completed, Ibrahim sat on a corner and then called, ‘You must come (you singular) for Hajj, come for Hajj.’ Had he called, ‘You must come (you plural)’ no one would go for Hajj except human beings that existed in those days. He, however, called, ‘You must come (you singular) for Hajj.’ In so doing, he made all people in the backs of men to answer the call of the caller to Allah, the Most Majestic, the Most Glorious. Those who said, ‘Labbayk, (here I am)’ ten times, perform Hajj ten times, those who said, ‘here I am’ five times perform Hajj five times, and those who did more do Hajj according to the number of saying, ‘here I am.’ Those who did not say, ‘here I am’, will not perform any Hajj.’”