To start with: This word has occurred in the Quran, in 87 different verses, and is an ambiguous term, i.e. it has more than one meaning.
Basically, the word Deen (دِيْن) means Religion, Law, Judgement, Result, Government, Method. The meaning Religion has occurred in the Quran in majority of the 87 verses, Law appears in 4 verses, Judgement appears in 17 verses, reward/result appears in 1 verse.
Let us analyze:
Religion as defined by “Idiomatic and Syntactic English Disctionary”, published by the Oxford University Press – is the belief in the existence of a Super-Natural ruling power, the creator and controller of the universe, who has given to man a spiritual nature which continues to exist after the death of the body.
The above definition looks like a jist of several verses of the Quran, but still does not convey the proper sense of the word “Deen”, because it is not only the belief in the Super-Natural power but as the Quran defines, it is submitting our will and attention to Allah, as described by the following verse:
وَمَنْ أَحْسَنُ دِينًا مِّمَّنْ أَسْلَمَ وَجْهَهُ لله وَهُوَ مُحْسِنٌ واتَّبَعَ مِلَّةَ إِبْرَاهِيمَ حَنِيفًا وَاتَّخَذَ اللّهُ إِبْرَاهِيمَ خَلِيلاً
And who is better in religion than he who submits his person (attention) to Allah and he is (also) a doer of good and follows the religion (dictated by) Ibrahim, the upright? And Allah had taken Ibrahim as a friend. Surah Nisa, C4, V125
وَمَا أُمِرُوا إِلَّا لِيَعْبُدُوا اللَّهَ مُخْلِصِينَ لَهُ الدِّينَ حُنَفَاء وَيُقِيمُوا الصَّلَاةَ وَيُؤْتُوا الزَّكَاةَ وَذَلِكَ دِينُ الْقَيِّمَةِ
And they were not ordered anything except that they should serve Allah, keeping religion exclusively for Him, being those who stand firm on that which is right, and (that they should) establish worship (salat) and give charity (zakat), and that is the established religion. Surah Al Bayyinah C98, V5
مَا تَعْبُدُونَ مِن دُونِهِ إِلاَّ أَسْمَاء سَمَّيْتُمُوهَا أَنتُمْ وَآبَآؤُكُم مَّا أَنزَلَ اللّهُ بِهَا مِن سُلْطَانٍ إِنِ الْحُكْمُ إِلاَّ لِلّهِ أَمَرَ أَلاَّ تَعْبُدُواْ إِلاَّ إِيَّاهُ ذَلِكَ الدِّينُ الْقَيِّمُ وَلَـكِنَّ أَكْثَرَ النَّاسِ لاَ يَعْلَمُونَ
You do not serve besides Him but names which you have named, you and your forefathers, for which Allah has not sent down any authority, the judgment is on one’s but Allah’s. He commands that you serve no one but Him alone, that’s the established religion but the majority of human beings does not know. Surah Yusuf, C12, V40
Yusuf AS was on the established Religion of his great grandfather Ibrahim AS which was a religion dictated by him. Allah SWT says: “You do not serve besides Him but names which you have named, you and your forefathers, for which Allah has not sent down any authority.” This means that if we are following anything apart from whatever Allah has sent is just names and nothing else. What is the authority which Allah SWT has sent down to be followed? What is the religion which Allah prefers:
…الْيَوْمَ أَكْمَلْتُ لَكُمْ دِينَكُمْ وَأَتْمَمْتُ عَلَيْكُمْ نِعْمَتِي وَرَضِيتُ لَكُمُ الإِسْلاَمَ دِينًا…
…This day I have perfected your religion for you and completed My favour on you and I have chosen ‘Al Islam’ as the religion for you… Surah Al Maidah, C5, V3
The above verse needs no explanation, the religion near Allah SWT is Al Islam. Here I would like to present an equation:
Islam = Quran + Sunnah. Quran is the Law, which is the theoretical part and Sunnah is the judgement, its the practical implementation of the Theoretical Laws, as shown by Prophet Muhammad SAWS.
The following verses throw more light on the subject:
شَرَعَ لَكُم مِّنَ الدِّينِ مَا وَصَّى بِهِ نُوحًا وَالَّذِي أَوْحَيْنَا إِلَيْكَ وَمَا وَصَّيْنَا بِهِ إِبْرَاهِيمَ وَمُوسَى وَعِيسَى أَنْ أَقِيمُوا الدِّينَ وَلَا تَتَفَرَّقُوا فِيهِ كَبُرَ عَلَى الْمُشْرِكِينَ مَا تَدْعُوهُمْ إِلَيْهِ اللَّهُ يَجْتَبِي إِلَيْهِ مَن يَشَاء وَيَهْدِي إِلَيْهِ مَن يُنِيبُ
He has given to you the (same) law of religion which He had enjoined on Nuh; and that which We communicated to you and that which We enjoined on Ibrahim and Musa and Isa (are also the same), that: “Establish the religion and do not be divided therein.” Hard on the polytheists is that which you invite them to. Allah chooses for Himself whom He wills and guides towards Himself, him who turns (to Him). Surah Ash Shura, C42, V13
وَلَهُ مَا فِي الْسَّمَاوَاتِ وَالأَرْضِ وَلَهُ الدِّينُ وَاصِبًا أَفَغَيْرَ اللّهِ تَتَّقُونَ
And whatever is in the skies and the earth is His and His is the law (that prevails) for ever. Will you then fear (someone) other than Allah? Surah An Nahl, C16, V52
In the above verse most of the translators of Quran have translated the word Deen as Religion, but Dr. Mir Aneesuddin has translated it as Law, i.e.”His is the Law (that prevails) forever. If we see the previous phrase, which says whatever in the skies and the earth is His, i.e to say that the skies and the earth are obeying the laws set by Allah SWT. Here the word Deen has been taken as Law, as can also be seen in the following verse:
إِنَّ عِدَّةَ الشُّهُورِ عِندَ اللّهِ اثْنَا عَشَرَ شَهْرًا فِي كِتَابِ اللّهِ يَوْمَ خَلَقَ السَّمَاوَات وَالأَرْضَ مِنْهَا أَرْبَعَةٌ حُرُمٌ ذَلِكَ الدِّينُ الْقَيِّمُ فَلاَ تَظْلِمُواْ فِيهِنَّ أَنفُسَكُمْ وَقَاتِلُواْ الْمُشْرِكِينَ كَآفَّةً كَمَا يُقَاتِلُونَكُمْ كَآفَّةً وَاعْلَمُواْ أَنَّ اللّهَ مَعَ الْمُتَّقِينَ
The number of months with Allah is certainly twelve months (in a year) in the ordinance of Allah (since) the day He created the skies and the earth, of them four are sacred (during which fighting is prohibited). That is the established law, so do not be unjust to yourselves concerning them. And fight the polytheists all together as they fight with you all together and know that Allah is certainly with those who guard (against evil). Surah Taubah, C9, V36
Here Allah SWT is referring to “The established Law”, the cycle on which the changing of seasons and 12 months are based, which is the established law, since the day He created the skies & the earth. Does this mean that the word Deen conveys the sense of scientific laws only? No, the following verse conveys the sense of law of king / law of the land:
الزَّانِيَةُ وَالزَّانِي فَاجْلِدُوا كُلَّ وَاحِدٍ مِّنْهُمَا مِئَةَ جَلْدَةٍ وَلَا تَأْخُذْكُم بِهِمَا رَأْفَةٌ فِي دِينِ اللَّهِ إِن كُنتُمْ تُؤْمِنُونَ بِاللَّهِ وَالْيَوْمِ الْآخِرِ وَلْيَشْهَدْ عَذَابَهُمَا طَائِفَةٌ مِّنَ الْمُؤْمِنِينَ
The adulteress and the adulterer, flog each of them (with) hundred stripes, and pity for them should not withhold you in (implementing) the law of Allah if you believe in Allah and the period hereafter, and let a party of believers witness their punishment. Surah Noor, C24, V2
Here Deen means law of Islam, i.e. the laws contained in Quran and the Sunnah of Prophet Muhammad SAWS, and in other places it means Judgement, as follows:
مَـالِكِ يَوْمِ الدِّينِ
the Master of the day of judgment. Surah Fatiha, C1, V3
أَئِذَا مِتْنَا وَكُنَّا تُرَابًا وَعِظَامًا أَئِنَّا لَمَدِينُونَ
that when we die and become(part of the) soil and bones, we will indeed be brought for judgment? Surah Saffat C37, V53
The meaning Judgement has been taken in the sense of ‘Day of resurrection’ except for the following verse
لَكُمْ دِينُكُمْ وَلِيَ دِينِ
For you your religion (or judgment) and for me my religion (or judgment). Surah Al Kafiroon C109, V6
This means for you what you judge and for me what I judge of the good. If we use any of the two meanings, religion or judgement it seems that we are giving them the authority to follow whichever religion they like. But if we take the meaning reward in this case, the verse would mean, for you your reward on the day of judgement and for me my reward on that day.
The following verse shows the meaning of Deen as reward:
يَوْمَئِذٍ يُوَفِّيهِمُ اللَّهُ دِينَهُمُ الْحَقَّ وَيَعْلَمُونَ أَنَّ اللَّهَ هُوَ الْحَقُّ الْمُبِينُ
On that day Allah will pay in full their due reward and they will come to know that Allah is the Manifest Truth. Surah Noor C24, V25
Therefore, the word Deen is vast in its meaning, i.e. it is a complete way of life which is to be followed in this world to be rewarded in full in the hereafter, which is why Allah SWT has mentioned the following purpose of this Religion of Peace:
هُوَ الَّذِي أَرْسَلَ رَسُولَهُ بِالْهُدَى وَدِينِ الْحَقِّ لِيُظْهِرَهُ عَلَى الدِّينِ كُلِّهِ وَلَوْ كَرِهَ الْمُشْرِكُونَ
He it is who sent His messenger with guidance and the true religion (Islam) that He may make it prevail over all religions though the polytheists may dislike. Surah Taubah C9, V33
With this I would like to end my talk and pray to Allah SWT that He make us follow the established religion, which is shown to us through Quran and Sunnah.
Wa Akhirud dawana anil Hamdulillahi Rabbil Alameen.