Imam Ali (peace be upon him): Faith, disbelief, polytheism, and their increase and decrease are as follows: faith in Allah is the highest of deeds and is at the loftiest rank; there is no station more honourable than it and its portion is greater than all others. It was said: 'O Amir al-Mu'minin (peace be upon him), is faith speech and deed, or speech alone?' He said: 'Faith is affirmation in the heart, confession by the tongue, and action by the limbs. Faith is entirely action. Faith is sometimes complete, sometimes half-complete, sometimes deficient, and sometimes increased — in such a way that this deficiency and increase can be clearly seen. Allah the Exalted has appointed a duty for each of the limbs and organs of the human being, and that duty has no connection with another organ... The Messenger of Allah (peace be upon him and his family) said: "Whoever meets Allah with complete faith is of the people of Paradise, and whoever squanders any of the obligations and disobeys the commands of Allah and commits what is forbidden, appears before Allah with deficient faith. Allah the Exalted said: 'This surah — whose faith among you has it increased?' [Say to them]: As for those who have believed, it has increased them in faith, and they [by the grace and mercy of Allah] rejoice." (Tawba/124) In another place He said: "The believers are only those whose hearts tremble when Allah is mentioned, and when His verses are recited to them, their faith is increased, and they place their trust only in their Lord." (Anfal/2) In another place He said: إِنَّهُمْ فِتْیَةٌ آمَنُوا بِرَبِّهِمْ وَ زِدْناهُمْ هُدیً [Surely they were youths who believed in their Lord and We increased them in guidance]. In another verse He said: "Those who are guided, Allah increases them in guidance and grants them the spirit of piety." (Muhammad/17) In another verse He said: "He it is who sent down tranquillity into the hearts of the believers, that they might increase in faith with their faith. And to Allah belong the hosts of the heavens and the earth, and Allah is Knowing, Wise." (Fath/4) And if all were equal in faith, no one would have superiority over another; with complete faith the believers enter Paradise and attain the ranks therein. If some people's faith is deficient, or they lose their faith, they enter the Fire.'