Physical action is an essential part of faith without which faith is not sound
Question

Some people think that physical righteous deeds are a prerequisite for the perfection of faith, but not one of the essential elements thereof, or in other words, they are not essential for the validity of faith. There has been a great deal of disagreement among people concerning this matter, so we hope that you can explain how valid this argument is, may Allah reward you. Please explain how important physical righteous deeds are to faith.
Praise be to Allah.What is indicated by the Quran and Sunnah, and the righteous early generations are agreed upon this, is that faith consists of both words and deeds, and may increase and decrease; there is no faith unless it is accompanied by actions, just as there is no faith unless it is accompanied by words. So faith is not valid unless both are present together. This is an issue that is known to Ahl as-Sunnah. As for the view that action is something required for the perfection of faith, this is the view of the Ash‘aris and others like them; it is well-known that the view of the Ash‘aris with regard to faith (eemaan) is one of the ideas of the Murji’ah.
Ash-Shaafa‘i (may Allah have mercy on him) said: The consensus of the Sahaabah and Taabi‘een, and those who came after them, and our contemporaries, is that faith consists of words, deeds and intentions, and none of the three is valid except with the others.
End quote from Sharh Usool I‘tiqaad Ahl as-Sunnah by al-Laalkaa’i (5/956); Majmoo‘ al-Fatawa (7/209).
Al-Aajurri (may Allah have mercy on him) said:
You should understand – may Allah have mercy on us and you – that the view of the Muslim scholars is that faith is obligatory for all people, and it consists of belief in the heart, affirmation on the tongue, and physical actions (righteous deeds).
Moreover, you should understand that having knowledge and belief in the heart is not sufficient unless it is accompanied by verbal affirmation of faith, and knowledge in the heart and verbal affirmation are not valid unless they are accompanied by physical action (righteous deeds). Once a person combines these three characteristics, then he is a believer. This is indicated by the Quran and Sunnah, and the views of the Muslim scholars."(Ash-Sharee‘ah  2/116).
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said: Based on this issue, we may conclude two things, the first of which has to do with visible disbelief and the second has to do with hidden disbelief.
As for the second (the issue of hidden disbelief), that is based on the view that faith consists of both words and deeds, as stated above. It is not possible for a man who believes firmly and strongly in his heart that Allah has enjoined upon him prayer, zakaah, fasting and Hajj, to live all his life without prostrating once to Allah, or fasting Ramadan, or giving zakaah for the sake of Allah, or going on pilgrimage to His House. That is not possible, and this cannot happen unless the person harbours hypocrisy and heresy in his heart. It does not happen when there is sound faith."(Majmoo‘ al-Fatawa 7/616).
Imam Muhammad ibn ‘Abd al-Wahhaab (may Allah have mercy on him) said: There is no difference of opinion among the ummah that Tawheed must exist in the heart, which is knowledge; and on the tongue, which is words (verbal affirmation); and in one’s actions, which is acting in accordance with the commands and prohibitions. If a person does not fulfil one of these three, then he is not a Muslim.
If he affirms Tawheed but does not act in accordance with it, then he is a stubborn disbeliever, like Pharaoh and Iblees. If he acts outwardly in accordance with Tawheed, but does not believe in it in his heart, then he is a pure hypocrite, worse than a disbeliever. And Allah knows best."(Ad-Durar as-Saniyyah fi’l-Ajwibah an-Najdiyyah 2/124).
He also said: You should understand – may Allah have mercy on you – that the validity of religious commitment depends on what is in the heart of belief, love and hate, and it depends on a person uttering (the word of Islam, the Shahaadah) and refraining from uttering words of disbelief, and it depends on physical deeds, by putting the pillars of Islam into action, and refraining from deeds that render one a disbeliever. If one of these three is missing, then the person becomes a disbeliever and an apostate."(Ad-Durar as-Saniyyah  10/87).
The scholars of Ahl as-Sunnah discussed this issue at length, including the fatwas issued by the Standing Committee that warn against some books which reiterate the view that physical actions (righteous deeds) are a precondition for the perfection of faith (and not an essential part thereof). The Committee has stated that that is the view of the Murji’ah. See: Fatawa al-Lajnah ad-Daa’imah (2/127-139, vol. 3).
According to Ahl as-Sunnah, physical action is an essential part of faith, without which faith is not valid, and a lack of physical action is indicative of a lack of faith in the heart, because they are strongly interconnected. Whoever thinks that there could be strong and sound faith without that leading to physical action (righteous deeds), even though he knows about his religious duties and is able to do them, is thinking that something impossible is possible, and is denying the connection between physical action and what is in the heart, and is following the blameworthy view of the Murji’ah.
And Allah knows best.