I would like to thank all the professors, scholars, and shaykhs who shared their knowledge with me over the past two and a half decades. I am most grateful to my friends and colleagues, Héctor Manzolillo, Barbara Castleton, and ‘Abdullah Shahin for constantly reviewing, correcting, and editing my works.

I am especially grateful to all my publishers for allowing me to reproduce my works in this medium and most honored that Ansariyan Publications has accepted to support this ambitious academic enterprise. Last, but certainly not least, I would like to thank my family for their loving support in the toughest of times.