"I believe that there is no deity except that in whom the Children of Israel believe, and I am of the Muslims." Surah 10:90
Iman is Belief, to understand the desired meaning of a word mentioned in the Quran or the Sunnah. There lies two basic meanings for Iman:
a. Belief and Acceptance
b. Adherence and Implementation
وَجَاوَزْنَا بِبَنِي إِسْرَائِيلَ الْبَحْرَ فَأَتْبَعَهُمْ فِرْعَوْنُ وَجُنُودُهُ بَغْيًا وَعَدْوًا ۖ حَتَّىٰ إِذَا أَدْرَكَهُ الْغَرَقُ قَالَ آمَنْتُ أَنَّهُ لَا إِلَٰهَ إِلَّا الَّذِي آمَنَتْ بِهِ بَنُو إِسْرَائِيلَ وَأَنَا مِنَ الْمُسْلِمِينَ
Surah 10:90; This means "I accept and affirm." I believe, or accept, is followed by a preposition that completes the meaning by explaining what belief was in. When one says "I believe in Allah" this means that the believes in His Names, Attributes and that he submits to His will. Like, When one says "I believe in the Messenger, who calls to Allah," this means "I believe in the revelation from Allah to the Prophet."
Believing in the heart and adhering to what this belief calls for, is one whole subject that cannot be divided. If belief exists in the heart, then this belief will lead to adhering and obeying (the commandments). This is an irrefutable fact Only those who are blinded by following their tradition for those who are ignorant, will reject its implications. What is important here is affirming that shunning adherence to the Commandments of Allah is punishable by the Fire of Hell.
What principles strengthen one's Iman?
1. To believe that Allah is the creator of this universe and the One who disposes its affairs.
2. To believe that Allah created the world for a wisdom.
3. To believe that the power to legislate and command is exclusively for Allah alone, for He is the Creator.
Unquestionaly, His is the creation and the command; blessed is Allah, Lord of the worlds. (Surah 7:54)
4. To worship Allah alone by obeying His commandments. To invoke Allah, in supplication, to have hope in Allah alone, and not to take any intermediaries between Allah and the believer.
5. To believe in Resurrection, Paradise, Hellfire and all historical events, or events of the future, that Allah told us.
The mind must be used to attain belief. First, one must know the truthfulness of the Messenger, in what he describes of Allah. Second, with regards to implementation and practicing, scholars differentiate between not practicing due to laziness, silly excuses or for being misguided, and between not practicing due to rejection and refuting the commandments. In short, Practicing is a necessity of belief. One must belief that a Wajib is an obligation, a Mustahab is recommended and a Haram is prohibited.
What Negotiates one's Iman?
1. Rejecting the Wisdom Behind the Commandments
2. Ruling by Other than What Allah Has Revealed
- Ruling by other than what Allah has revealed, believing that these rules are better than Allah's ,constitutes Kufr.
- Ruling by other than what Allah has revealed believing that these rules are equal to Allah's, also constitutes Kufr.
- Believing that Allah's Rule is the best and the truth, and that whatever defies it is false and misguided, yet ruling by other than what Allah has revealed because of following desires or for money or positions to be gained.
3. Ridiculing a Muslim for His Islam
- Ridiculing Muslims may happen because of their looks, behavior or conduct.
- Ridiculing Muslims may happen because he is a good Muslim, following Allah's Path, or because he is performing an act of Iman that Allah has Commanded.
(83:29) Behold, the wicked were wont to laugh at the believers: (83:30) when they passed by them they winked, (83:31) and when they went back to their families, they went back jesting,(83:32) and when they saw the believers, they said: “Lo! These are the erring ones”;(83:33) (they said so although) they had not been appointed watchers over them.
4.Loyalty to Allah's Enemies
5. To be Pleased When Sin is Widespread
Iman requires loving Allah's Laws and Commandments and seeking to implement them till Allah's word is the Highest, and the word Kufr is the lowest. Kufr, in Arabic means to cover something. Disbelievers are called Kuffar because they know Tawheed (monotheism), yet they insist on their disbelief and Kufr. They cover Iman with disbelief. Kufr is rejecting the truth after knowing it. If one rejects any matter of faith or does any type of kufr, out of ignorance, thinking that Islam permits it, then he is not Kafir. Rejecting the truth after knowing it out of arrogance and rebellion, not out of ignorance is a Kafir. For example, father of disbelievers on earth, pharaoh, who disbelieved out of arrogance and rebel.
A Muslim must not be considered sinful and misguided until the truth is shown to him and he still rejects it. Allah says in the Qurah Surah Tawbah:
113. It is not (proper) for the Prophet and those who believe to ask Allah's forgiveness for the Mushrikin, even though they be of kin, after it has become clear to them that they are the dwellers of the Fire (because they died in a state of disbelief). 114. And Ibrahim's invoking (of Allah) for his father's forgiveness was only because of a promise he ﴿Ibrahim﴾ had made to him (his father). But when it became clear to him ﴿Ibrahim﴾ that he (his father) is an enemy of Allah, he dissociated himself from him. Verily, Ibrahim was Awwah and forbearing. 115. And Allah will never lead a people astray after He has guided them until He makes clear to them what they should avoid. Verily, Allah is the All-Knower of everything. 116. Indeed to Allah belongs the dominion of the heavens and the earth, He gives life and He causes death. And besides Allah you have neither any protector nor any helper.
If the heart is not moved by sin, by hating it and whoever performs it, then this heart is pleased with sin. To be pleased with sin is approving of it. To approve of sin is rejection of Religion of Allah, the Praised One, and of Iman in HIm. If satisfaction and approval is followed by love, obedience, praise and blessing of sin, then two crimes exist:
1. Kufr and rejection of Allah.
2. Hindering from the Path of Allah.
Accepting the spread of sins and misguidance is a result of seeking the demise of Allah's Word and victory of Kafir word.This is the exact opposite of Iman. Iman requires one to seek to make Allah's Word the Highest and Kafir word the lowest.
And of His signs is the creation of the heavens and the earth and the diversity of your languages and your colors. Indeed in that are signs for those of knowledge. (Surah 30:22)
Rest Allah knows best.
Source: Quran, Sunnah, In the shade of the Quran, The Clear Distinction Between Iman & Kufr by Abdur Rahman Abdul Khaliq.