Is it permissible to conceal his faith and say that he is a Christian?
Question

Hello. I would like to ask you, I am secretly Muslim and am hiding my faith from my Christian family. Is it regarded as disbelief (kufr) if I tell them “I am Christian”?
Praise be to Allah.Firstly:
We congratulate you, our Muslim sister, for what Allah has honoured you with and blessed you with, and for His opening your heart to guidance and the religion of truth. This is the greatest blessing that has been bestowed upon you since your mother gave birth to you, so you should praise Allah greatly and ask your Lord to make you steadfast in adhering to guidance and the religion of truth so long as you remain in this world, and to grant you a good end, and thus grant you the best in both this world and the hereafter. We also give you the glad tidings that the Prophet (blessings and peace of Allah be upon him) gave to anyone who believes in the religion of Islam and follows its Prophet, and was a believer in a previous Book, whether he was a Jew or a Christian.
It was narrated from Abu Musa al-Ash‘ari (may Allah be pleased with him) that the Messenger of Allah (blessings and peace of Allah be upon him) said: “There are three who will be given a double reward: a man from among the people of the Book who believed in his Prophet, then lived to see the Prophet (S) and followed him and believed in him– he will have a double reward…”
Narrated by al-Bukhari (3011) and Muslim (154).
Secondly:
Undoubtedly one of the greatest difficulties that the new Muslim may face is confronting his family and social circle who are following a religion other than Islam. This may be more difficult and more vicious in Arab countries and eastern countries in general, to the extent that it may lead to pressure to give up his religion and attempts to make him recant by any possible means. But these concerns about family opposition and social pressure should be analysed within a proper framework, which will help you to plan your next step and will help you to remain steadfast with strong resolve to persevere and do everything that is required of you.
This is akin to the traveller’s concerns about the risks of travel, and the troubles and difficulties he will face, but he has no choice but to start his journey. Therefore he takes appropriate measures, prepares his provisions and chooses his travel companion, then he sets out… Despite the fears, people still travel.
And it is akin to the concerns of the sick person who is about to die, and faces surgeries and treatments in which there may be a great deal of pain and fear, but he has no choice but to bear that with patience, or else he is going to die.
Your need to start your journey towards the Lord of the Worlds surpasses the need of all these people (travellers and sick people); it surpasses the need of one who is about to drown and die, then a lifebelt is thrown to him; it surpasses the need of the thirsty person for cool water on a hot day; it surpasses any need that any human could think of or imagine.
Thirdly:
When we understand the pressure of the social environment, we will realise that this environment will, in many instances, force you to conceal your Islam and even make you pretend to others that you are still following their religion. So there is no blame on you if you tell them that you are a “Christian” and – in such cases – you will be regarded as one who had no choice and was compelled to do that. Allah, may He be exalted, says by way of giving a concession to His slaves (interpretation of the meaning):
{Those who disbelieve in Allah after having believed – except one who is compelled while his heart remains steadfast in faith – and willingly open their hearts to disbelief, upon them will be the wrath of Allah, and theirs will be a grievous punishment} [Al-Nahl 16:106].
Ibn Kathir (may Allah have mercy on him) said: Regarding the words {except one who is compelled while his heart remains steadfast in faith}, this is an exception from what is mentioned at the beginning of the verse, for the one who only utters words in order to go along with the polytheists verbally, under duress, because of what he has suffered of beatings and harm, but in his heart he rejects what he is saying and he remains steadfast in his belief in Allah and His Messenger.
Al-‘Awfi narrated from Ibn ‘Abbas that this verse was revealed concerning ‘Ammar ibn Yasir, when the polytheists tortured him in order to make him disbelieve in Muhammad (blessings and peace of Allah be upon him), and he went along with them in that unwillingly,  because he was forced to do so. He came and apologised to the Prophet (blessings and peace of Allah be upon him), then Allah revealed this verse. This was stated by al-Sha‘bi, Abu Malik and Qatadah.
Ibn Jarir said: Ibn ‘Abd al-A‘la told us: Muhammad ibn Thawr told us, from Ma‘mar, from ‘Abd al-Karim al-Jazari, from Abu ‘Ubaydah ibn Muhammad ibn ‘Ammar ibn Yasir, who said: The polytheists seized ‘Ammar ibn Yasir and tortured him until he gave them some of what they wanted. He complained about that to the Prophet (blessings and peace of Allah be upon him), and the Prophet (blessings and peace of Allah be upon him) said: “How do you find your heart?” He said: It is steadfast in faith. The Prophet (blessings and peace of Allah be upon him) said: “If they do that again, then do the same thing again.”
Al-Bayhaqi narrated a more detailed report, in which it says that he reviled the Prophet (blessings and peace of Allah be upon him) and spoke well of their gods, and that he said: O Messenger of Allah, I was not left alone until I reviled you and spoke well of their gods. He said:  “How do you find your heart?” He said: It is steadfast in faith. The Prophet (blessings and peace of Allah be upon him) said: “If they do that again, then do the same thing again.” Concerning that, Allah revealed the words (interpretation of the meaning): {except one who is compelled while his heart remains steadfast in faith}."(Tafsir Ibn Kathir, 4/605).
The best for you is to intend, every time you say that you are a “Christian”, that you are one of the followers of the Messiah ‘Isa ibn Maryam (Jesus son of Mary – peace be upon him), for the Messiah ‘Isa (peace be upon him) was a monotheist and a Muslim, and he did not bring the religion of the cross; he did not want the people to worship him instead of Allah.
Allah may He be exalted, says (interpretation of the meaning):
{When Allah says: O ‘Isa son of Maryam, did you say to people: Take me and my mother as two gods besides Allah? He [‘Isa] will say: Glory be to You! It would not have been proper for me to say that which I had no right [to say]. If I had said it, You would surely have known it. You know all that I know, whereas I do not know what You know. Verily, You alone are the Knower of the unseen.
I said nothing to them except that which You commanded me [to say]: Worship Allah, my Lord and your Lord. I watched over them whilst I was amongst them, then when You took me up to You, You [alone] were the Watcher over them, and You are Witness over all things} [Al-Ma’idah 5:116-117].
The Messiah (peace be upon him) foretold the coming of the Prophet of Islam and his religion, and he took a covenant from his people that they would follow the Prophet of Allah (blessings and peace of Allah be upon him).
But those among the Jews and Christians who associate others with Allah are the ones who concealed his prophecies and went against the covenant with him.
Allah, may He be exalted, says (interpretation of the meaning):
{And [remember] when ‘Isaâ ibn Maryam said: O Children of Israel, verily I am the Messenger of Allah to you, confirming what came before me of the Torah, and bringing glad tidings of a Messenger to come after me, whose name will be Ahmad. But when he came to them with clear signs, they said: This is obviously magic!
Who does greater wrong than he who fabricates lies against Allah when he is called to Islam? And Allah does not guide people who are given to wrongdoing.
They want to extinguish Allah’s light with their utterances, but Allah will perfect His light, even though the disbelievers hate it} [Al-Saff 61:6-9].
Whatever the case, there is no blame on you if you say these words to your family or those from whom you fear trouble regarding your religion in your social circle. Our advice to you is to conceal your Islam from them, until Allah grants you a way out.
Please see also the answer to question no. 434525 .
And Allah knows best.