26.1 ISLAAM.
26.1.1 LINGUISTICALLY
means "submission" [al Inqiyaad]
26.1.2 IN THE SHAREE'AH
it means "the surrendering of the slave, to Allaah, both outwardly and inwardly by carrying out its commandments and avoiding its prohibitions." Hence it comprises the whole Religion. See (5):3; (3):85.
26.2 EEMAAN.
26.2.1 LINGUISTICALLY
means "affirmation" [at-Tasdeeq]. See (12):17.
26.2.2 IN THE SHAREE'AH
It means "the affirmation of the heart that necessitates speech and action, i.e. belief of the heart, speech of the tongue, and action of the heart and limbs."
See hadeeth: "Eemaan is that you believe in Allaah, His Angels,...", and hadeeth: "Eemaan consists of seventy odd branches...".
Hence Eemaan comprises the whole Religion, and hence is not different from Islaam, in this context.
26.3 ISLAAM & EEMAAN.
When the two terms are found together then Eemaan is taken to mean the inward submission [affirmation and action of the heart] - which will only eminate from a believer [Mu-min], while Islaam is taken to mean the outward submission [speech of the tongue and action of the limbs] - which eminates from someone who's complete or weak in Eemaan, or even void of it [e.g. a hypocrite].
See (49):14; (8):2-4
Hence the meaning of Eemaan is superior for every Mu-min is a Muslim, but the reverse is not the case.
26.4 THE INCREASE & DECREASE OF EEMAAN.
Ahl-us-Sunnah are agreed that Eemaan increase and decreases. There are many narrations from the Salaf concerning this.
See (48):4 & many others, and hadeeth: "I have not seen anyone more defecient in intellect and religion..." and others.
Two sects have differed from this:
26.4.1 THE EXTREME MUJI-AH
who believe that Eemaan is affirmation of the heart only and this affirmation does not differ. So to them, the Faasiq and the just honest man are the same in terms of Eemaan.
26.4.2 THE WA'EEDEEYAH
from the Mu'tazilah and Khawaarij, who expel any one who has done a major sin from having any Eemaan. So they say Eemaan is either completely there or not, and has no levels.
26.4.3 THE TEXTS AND THE INTELLECT REFUTE BOTH OF
THESE:
26.4.3.1 Refuting the Murji-ah.
(1) Saying Eemaan is only the affirmation of the heart contradicts the Book and the Sunnah, for they show that speech and action are also included.
(2) Saying affirmation of the heart does not differ among the people condradicts all sense, for we all know that affirmation is based on knowledge and that the people differ in the amount and quality of knowledge they have, and so the certainty people have as a result of their knowledge must also differ.
(3) Even an individual feels that with different times and situations he strength of certainly changes.
(4) How can any mind accept that the evil sinning Muslim and the obedient pious worshipping Muslim are the same in Eemaan?
26.4.3.2 Refuting the Wa'eedeeyah.
(1) Saying that a person is expelled from having Eemaan due to doing a major sin, contradicts the Book and the Sunnah.
(2) And concerning their belief that no levels of Eemaan exist between having it completely and not having it at all, then this is refuted by points (2) & (4) of 26.3.2.1.
26.4.4 THINGS THAT INCREASE EEMAAN.
26.4.4.1 Knowing Allaah's Names &
Attributes.
26.4.4.2 Contemplating over the Aayaat of Allaah that
relate to His Decree and His Laws.
26.4.4.3 Doing Acts of Obedience - with Eemaan
increasing according to the sincerity and correctness of the action done, the
type of deed done [e.g. if obligatory or recommended], and the amount of deed
done.
26.4.4.4 Leaving a Sin Due to Fear of Allaah - with
Eemaan increasing according to the strength of the temptation being
overcome.
26.4.5 THINGS THAT DECREASE EEMAAN.
26.4.5.1 Being Ignorant of Allaah's Names &
Attributes.
26.4.5.2 Disregarding & Turning Away From the
Aayaat of Allaah that relate to His Decree and Laws.
26.4.5.3 Doing Sins
with Eemaan decreasing according to the type of evil [e.g. if major or not, or if Kufr or Shirk], the amount of sin done, the lack of regret & importance when doing the sin, and according to the lack of temptations calling to the sin [e.g. refer to hadeeth: "Allaah will not speak to or look at or purify three on the Day of Ressurection..."].
26.4.5.4 Leaving off Acts of Obedience
with Eemaan decreasing according to how certain one is that the deed is part of obedience. And one could be punished for this [i.e. where an obligatory act is not done with no excuse from the Sharee'ah], or not punished [i.e. where one has a physical or Sharee'ah proof for not doing the act - e.g. a woman who misses the Salaah when in her periods, or anyone who does not pray Salaat-ud-Duhaa].