Faith (īmān) is the unwavering belief and absolute acceptance of all that Allāh and His Messenger have commanded us to have faith in, submitting to it both inwardly and outwardly. It is an acceptance and belief of the heart that incorporates acts of the heart as well as acts of the body. Therefore, it covers observing the whole of this religion.
This is why the Imāms and Salaf used to say, ‘Faith is statement of the heart and tongue, and it is action of the heart, tongue and limbs.’
Faith is made up of statement, action and belief; it increases through obedience and decreases through disobedience. It covers the articles of creed, and the resultant conduct and deeds demanded by it.
Affirming and accepting Allāh’s Beautiful Names, His perfect and sublime Attributes, and all His actions is one of the greatest principles of faith. Similarly, acknowledging the rights that are due to Allāh alone: taking Him as god and worshipping Him both outwardly and inwardly is one of the principles of faith. Accepting everything that Allāh told us of concerning His Angels and forces, of what has happened and is to happen, and the Last Day is one of the principles of faith. Having faith in all the Messengers (salawātullāhi wa salāmuhu ʿalayhim), and in all their praiseworthy qualities described in the Book and Sunnah is one of the principles of faith. One of the greatest principles of faith is to believe in the oneness of Allāh completely and that only He is deserving worship, and then to worship Him alone without associating any partners with Him, making the religion sincerely for Him and observing the outward laws of Islām and its inward realities.
All of the above form the foundations of faith. This is why the outcome of faith is entry into Paradise and safety from the Fire. It leads to Allāh’s good pleasure, success and happiness.
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Allāh says, “Those who have faith and do righteous actions – they are the best of creatures. Their reward is with their Lord: Gardens of Paradise with rivers flowing under them, remaining in them timelessly, forever. Allāh is pleased with them and they are pleased with Him. That is for those who fear Allāh.” (Q98: 7-8)