Protection means: the act of protecting somebody/something; the state of being protected.
[Oxford Advanced Learner’s Dictionary, p:1197]
Religion means: the belief in the existence of a god, and the activities that are connected with the worship of them, or in the teachings of a spiritual leader.
[Oxford Advanced Learner’s Dictionary, p:1263]

The word “deen“ in Arabic means ‘religion‘ in its most general sense, the plural of which is Adyaan.

Allah said:

إِنَّ الدِّينَ عِنْدَ اللَّهِ الْإِسْلَام

“Truly, the religion with Allah is Islam”. [Qur’an 3:19].
“al-Deen” (The Religion) then the intended meaning is the religion of Islam. As Allah says in the Qur’an “Verily, the religion (al-Deen) with God is Islam” [Qur’an 3:19].

How to protect the religion?

1. BELIEF IN THE FOUNDATIONS OF THE RELIGION:

‘Umar bin Al-Khattab (May Allah be pleased with them) said:
Once we were sitting in the company of Messenger of Allah (ﷺ) when there appeared a man dressed in very white clothes and having extraordinary black hair. No signs of fatigue of journey appeared on him and he was known to none of us. He sat down facing the Prophet (ﷺ) leaning his knees against the knees of the Prophet (ﷺ) and placing both of his palms over his two thighs and said, “O Muhammad (ﷺ)! Tell me about Islam”. He (ﷺ) replied, “Islam is to testify that none has the right to be worshipped but Allah, and that Muhammad (ﷺ) is the Messenger of Allah; that you observe Salat (prayers), pay Zakat, observe Saum (fasting) of Ramadan and perform Hajj (pilgrimage) of the House, provided you have resources of making journey to it.” He replied: “You have spoken the truth.” We were surprised to see that he had asked him and confirmed the correctness of the answers. He then enquired: “Tell me about Iman.” He (ﷺ) said: “It is to believe in Allah, His angels, His Books, His Messengers and the Last Day and that you believe in preordainment (destiny), its bad and good consequences.” He said, “You have spoken the truth.” He then enquired: “Tell me about Ihsan.” He (ﷺ) said, “It is to worship Allah as if you are seeing Him….” [Muslim, Hadith 60]

2. ADHERENCE TO THE FOUNDATIONS OF WORSHIP:

It is narrated on the authority of ‘Abdullah son of ‘Umar that the Messenger of Allah (ﷺ) said:(The superstructure of) al-Islam is raised on five (pillars), testifying (the fact) that there is no god but Allah, that Muhammad is His bondsman and messenger, and the establishment of prayer, payment of Zakat, Pilgrimage to the House (Ka’ba) and the fast of Ramadan.” [Muslim, Hadith 21]

3. SEEKING KNOWLEDGE:

قال الله:{وَقُلْ رَبِّ زِدْنِي عِلْمًا} [طه: 114]

Allah said “: say: “My Lord! Increase me in knowledge.” [Qur’an 20:114]

It was narrated from Anas bin Malik that the Messenger of Allah (ﷺ) said:”Seeking knowledge is a duty upon every Muslim” [Sunan Ibn Majah, Hadith 224].

4. TEACHING THE RELIGION:

We are encouraged to spread the teachings of God’s final revelation by word and by deed.

قال الله:{ادْعُ إِلَى سَبِيلِ رَبِّكَ بِالْحِكْمَةِ وَالْمَوْعِظَةِ الْحَسَنَةِ} [النحل: 125]

Allah said: “Invite (mankind, O Muhammad SAW) to the Way of your Lord (i.e. Islam) with wisdom (i.e. with the Divine Inspiration and the Quran) and fair preaching”. [ Qur’an 16:125].

Abu Sa`id Al-Khudri (May Allah be pleased with him) reported: The Prophet ((ﷺ) said, “Beware of sitting on roads (ways).” The people said: “We have but them as sitting places.” Messenger of Allah (ﷺ) said, “If you have to sit there, then observe the rights of the way”. They asked, “What are the rights of the way?” He (ﷺ) said, “To lower your gaze (on seeing what is illegal to look at), and (removal of harmful objects), returning greetings, enjoining good and forbidding wrong”.
[Al-Bukhari and Muslim].

5. DEFENDING OF ISLAM:

Nu`man bin Bashir (May Allah be pleased with him) reported: The Prophet (ﷺ) said, “The likeness of the man who observes the limits prescribed by Allah and that of the man who transgresses them is like the people who get on board a ship after casting lots. Some of them are in its lower deck and some of them in its upper (deck). Those who are in its lower (deck), when they require water, go to the occupants of the upper deck, and say to them : `If we make a hole in the bottom of the ship, we shall not harm you.’ If they (the occupants of the upper deck) leave them to carry out their design they all will be drowned. But if they do not let them go ahead (with their plan), all of them will remain safe”. [Al-Bukhari, Hadith 187].

We learn from this Hadith that the consequences of committing acts which are forbidden in Islam.

Preserving Islam is by learning it, teaching it, spreading it and defending it.