Sayyiduna Abu Razin Aqili (may Allah be pleased with him) says: I came to the Messenger of Allah (peace and blessings be upon him) and I said: "O Messenger of Allah! What is faith?" He (peace and blessings be upon him) said: "It is that you bear witness that Allah Almighty alone is the true deity, He is One and Unique, He has no partner, and that Muhammad (peace and blessings be upon him) is His servant and Messenger, and that Allah and His Messenger are dearer to you than all other things, and that you would prefer to be burned in the fire rather than associate partners with Allah, and that you love no one who is not a relative except for the sake of Allah Almighty. When this happens, that is, when you accomplish these matters, then the love of faith will enter your heart just as the love of water penetrates the heart of a thirsty person on a very hot day." I said: "O Messenger of Allah! How will I know that I am a believer?" He (peace and blessings be upon him) said: "Any person from my Ummah who does a good deed, while knowing that it is a good deed and that Allah Almighty is the One who will reward him for it, and likewise, any person who commits a sin, while knowing that it is indeed a sin, and then seeks forgiveness from Allah Almighty, and knows that only He forgives, then he is a believer."