All perfect praise is due to Allaah, Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, is His slave and Messenger.
Islam literally means submission and adherence to the commands of Allaah The Almighty. In this sense, Islam includes apparent acts of worship, as stated by the Prophet, SallAllahu Alaihi Wa Sallam, in the Hadeeth of Jibreel (Gabriel). The Prophet, SallAllahu Alaihi Wa Sallam, stated that Islam is to testify that there is no deity worthy of worship but Allaah and that Muhammad is the Messenger of Allaah, and performing Salaah (prayer), giving Zakaah (obligatory almsgiving), fasting the month of Ramadhaan and performing Hajj (pilgrimage), for those who can afford it.
Eemaan [faith] refers to belief and the Prophet, SallAllahu Alaihi Wa Sallam, defined it in the Hadeeth above . He stated that Eemaan is to believe in Allaah, His angels, His Books, His Messengers, the Hereafter and Fate, whether good or bad. Eemaan in this sense is hidden. If both are mentioned separately they refer to one another. In other words, if we call someone a Muslim, it means that this person believes, and vice versa.
Scholars conclude that if both Islam and Eimaan are mentioned in the same context, each has its distinctive meaning, as mentioned in the Hadeeth, whereas each term will have the meaning of both terms if mentioned independently in a context. Therefore, Islam and Eemaan (faith) are interrelated as well as inseparable. The deeds of the person who declares the two testimonies of faith, performs Salaah (prayers), gives Zakaah (obligatory almsgiving) etc. are of no significance unless he has innermost belief in Allaah, His angels, His Books, His Messengers, the Hereafter etc. Otherwise, the person will be a hypocrite who says with his tongue what is not in his heart. Similarly, a person’s belief in Allaah, His angels, His Books etc. will be useless and not avail him if he does not act according to the two testimonies of faith, perform his prayers etc. Allaah the Almighty Says:
وَجَحَدُوا۟ بِهَا وَٱسْتَيْقَنَتْهَآ أَنفُسُهُمْ ظُلْمًا وَعُلُوًّا ۚ فَٱنظُرْ كَيْفَ كَانَ عَٰقِبَةُ ٱلْمُفْسِدِينَ
“And they rejected them, while their [inner] selves were convinced thereof, out of injustice and haughtiness. So see how was the end of the corrupters.”
A Muslim may be described as a disbeliever if he practices Islamic rituals before people but his heart is not convinced about what he does or does not believe in what he does. This is similar to the case of the hypocrites and the Bedouins at the dawn of Islam who embraced Islam and said that they were believers just to gain protection for themselves and their wealth. Allaah the Almighty Says:
قَالَتِ ٱلْأَعْرَابُ ءَامَنَّا ۖ قُل لَّمْ تُؤْمِنُوا۟ وَلَٰكِن قُولُوٓا۟ أَسْلَمْنَا وَلَمَّا يَدْخُلِ ٱلْإِيمَٰنُ فِى قُلُوبِكُمْ ۖ وَإِن تُطِيعُوا۟ ٱللَّهَ وَرَسُولَهُۥ لَا يَلِتْكُم مِّنْ أَعْمَٰلِكُمْ شَيْـًٔا ۚ ٌ
“The Bedouins say, “We have believed.” Say, “You have not [yet] believed; but say [instead], ‘We have submitted,’ for faith has not yet entered your hearts.”
A person cannot be described as a believer unless he is originally a Muslim, because Eimaan is a special degree, whereas Islam is a general description for every person who declares the two testimonies of faith and applies the apparent ordinances of Islam. Furthermore, a Muslim may not be a believer, but a believer is certainly a Muslim.