Faith (Imaan) is statement and deed. It increases and diminishes.
Explanation: From the ways of People of Narrations is that faith [consists] of speech, action and belief; it increases with obedience and decrease with disobedience.
According to Ahlus Sunnah faith is of three conditions:
- Affirmation of the heart
- Speech of the tongue
- Actions of the limbs
One cannot be a believer until he possesses these three traits. If one commits major disbelief in any of these conditions then he has left the fold of Islam.
The evidences for this are in the Quran, Sunnah and the statements of the Muslim scholars.
Evidence for Imaan to be Affirmation of the Heart:
The evidence that affirmation of the heart is an essential condition of Iman is in the following verses of Allah:
“O Messenger (Muhammad)! Let not those who hurry to fall into disbelief grieve you, of such who say: “We believe” with their mouths but their hearts have no faith. And of the Jews are men who listen much and eagerly to lies – listen to others who have not come to you. They change the words from their places; they say, “If you are given this, take it, but if you are not given this, then beware!” And whomsoever Allah wants to put in Al-Fitnah [error, because of his rejecting the Faith], you can do nothing for him against Allah. Those are the ones whose hearts Allah does not want to purify (from disbelief and hypocrisy); for them there is a disgrace in this world, and in the Hereafter a great torment.”
Also He says: “Whoever disbelieved in Allah after his belief, except him who is forced thereto and whose heart is at rest with Faith, but such as open their breasts to disbelief, on them is wrath from Allah, and theirs will be a great torment.”
These evidences state that the heart must have Iman and that this must manifest in two ways:
The heart must affirm the Statements of the tongue and the actions.
Evidence for Iman to be Statements of the Tongue:
As for the evidence that Statements of the tongue is an essential condition of Iman it is found in the saying of Allah:
“Say (O Muhammad): “We believe in Allah and in what has been sent down to us, and what was sent down to Ibrahim (Abraham), Isma’il (Ishmael), Ishaq (Isaac), Ya’qub (Jacob) and Al-Asbat [the offspring twelve sons of Ya’qub (Jacob)] and what was given to Musa (Moses), ‘Isa (Jesus) and the Prophets from their Lord. We make no distinction between one another among them and to Him (Allah) we have submitted (in Islam).”
Also evidence can be take from the authentic narration: Abdullah Ibn Muhammad Al-Musnadi narrated from Abu Rawh Al-Harami Ibn ‘Umarah from Shu’ba from Waqid Ibn Muhammad who heard from his father from Ibn ‘Umar that the Messenger of Allah said, “I have been commanded to fight the people until they testify that there is no deity worthy of worship except Allah, and that Muhammad is the Messenger of Allah, and establish the prayer, and pay the zakat. If they do that, their lives and property are protected from me except for the right of Islam, and their reckoning is up to Allah.”
Therefore, Iman by the statements of the tongue is obligatory.
Evidence for Iman to be Actions of the Limbs:
As for actions of the bodily limbs being part of Iman it is concurrent with the affirmation of the heart and the statements of the tongue.
Allah says, “O you who have believed! Bow down, and prostrate yourselves, and worship your Lord and do good that you may be successful.”
And Allah says in several places in the Quran: “And perform As-Salat (Iqamat-as-Salat), and give Zakat, and bow down (or submit yourselves with obedience to Allah) along with Ar-Raki’un.”
Likewise the actions of the one who is fasting, doing Hajj, doing Jihad and other actions from the rituals of Islam.
Imam Al-Laalikaa’ee (d. 418H) reports that Abdur-Razzaaq as-San’aanee (d. 211H) said: I met sixty two Shouykh, amongst them were:
- al-Waleed bin Muhammad al-Qurashee,
- Yazeed ibn as-Saa’ib,
- Hammaad bin Salamah,
- Hammaad bin Zaid,
- Sufyaan bin Uyainah,
- Shu’ayb bin Harb,
- Wakee’ bin al-Jarraah,
- Maalik bin Anas,
- Ibn Abee Laylaa,
- Isma’eel bin Ayyaash,
- al-Waleed ibn Muslim
And those I have not named all of them saying: “Faith consists of speech and action, it increases and decreases.”
Iman either Increases or Decreases
Imaan increases by obedience and decreases by disobedience. This is the saying of Ahl al-Sunnah wal Jamâ’ah and it is the correct position on the matter. There are many evidences that support it.
Allah says: “It is He Who sent down tranquility into the hearts of the believers, that they may add faith to their faith”
Allah says: “For believers are those who, when Allah is mentioned, fell a tremor in their hearts, and when they hear His revelations rehearsed, find their faith strengthened and put (all) their trust in their Lord”
Allah says: “Those to whom hypocrites said, “Indeed, the people have gathered against you, so fear them.” But it [merely] increased them in faith, and they said, “Sufficient for us is Allah, and [He is] the best Disposer of affairs.”
The Prophet (peace be upon him) said: “Faith is seventy-odd branches, the greatest of which is to say ‘There is no God but Allah’ and the lowest of which is to remove an obstacle from the road.”
The Prophet (peace be upon him) said: “Modesty is a branch of faith.”
The Prophet (peace be upon him) said: “Whoever among you sees something false then he should change it by his hand, if cannot, by his tongue, and if cannot by his heart and that is the least faith.” and in another narration, it reads: “There is no single atom of faith after that.”
 Surah Maa’idah: 41
 Surah Nahl: 106
 Surah Imran: 84
 Recorded by Bukhari
 Surah Hajj: 77
 Surah Baqarah: 43
 Sharh Usool I’tiqaad Ahlus –Sunnah (5/958)
 Surah al-Fath: 4
 Sûrah al-Anfâl: 2
 Sûrah Al-`Imrân: 173
 Recorded in Sahîh al-Bukhârî and Sahîh Muslim
 Recorded in Sahîh al-Bukhârî and Sahîh Muslim
 Recorded in Sahih Muslim