Praise be to Allah.
The cross is one of the obvious symbols of disbelief, as Ibn al-Qayyim (may Allah have mercy on him) said in Ahkaam Ahl adh-Dhimmah (3/1240). Therefore there was no difference of opinion among the scholars that it is prohibited to wear it.
It says in al-Mawsoo‘ah al-Fiqhiyyah al-Kuwaitiyyah (12/88): It is not permissible for the Muslim to make a cross and it is not permissible for him to issue instructions for a cross to be made. What is meant is making a cross that is symbolic of the crucifixion, and he should not keep it, whether he wears it or sets it up, or he does neither.
Many of the scholars have clearly stated that the one who does that is a disbeliever.
It says in al-Fataawa al-Hindiyyah, one of the books of the Hanafi madhhab (2/276): A person becomes a disbeliever if he puts a Zoroastrian cap on his head, according to the correct view, except in the case of necessity to protect himself from heat or cold; or if he puts a zunnaar [a kind of belt that was worn by non-Muslims in the past] around his waist, unless he does that by way of deceit at a time of war or he is acting as a scout ahead of the Muslim army. End quote.
It says in Majma‘ al-Anhur fi Sharh Multaqa al-Abhur, which is also a Hanafi book (1/698): A person becomes a disbeliever if he puts a Zoroastrian cap on his head, according to the correct view, except if it is for the purpose of freeing a Muslim prisoner or it is a case of necessity to protect himself from heat or cold, according to some scholars. End quote.
Al-Qaadi ‘Iyaad said: Similarly, we regard as a disbeliever anyone who does any action that the Muslims are unanimously agreed can only come from a disbeliever, even if the one who does it openly professes Islam, yet he does that action…
… Such as prostrating to an idol, or to the sun or moon, or to a cross, or to fire, or going to churches and synagogues with their congregations, or wearing their garments, such as wearing their zunnaar (distinctive belts) or cutting the hair in the style of a monk (tonsure).
The Muslims are unanimously agreed that such things are only done by a disbeliever, and that these actions are symbols of disbelief, even if the one who does them openly professes Islam.
End quote from ash-Shifa bi Ta‘reef Huqooq al-Mustafa – Mahdhoof al-Asaaneed (2/611).
The scholars of the Standing Committee for Issuing Fatwas were asked about the ruling on wearing a cross and they replied:
If the ruling on wearing a cross is explained to him, and he is told that it is a symbol of the Christians and is an indication that the wearer is content to be regarded as one of them and that he is content with what they believe in, yet he persists in that, he is to be deemed a disbeliever, because Allah, may He be glorified and exalted, says (interpretation of the meaning):
“O you who believe! Take not the Jews and the Christians as Auliyâ’ (friends, protectors, helpers), they are but Auliyâ’ of each other. And if any amongst you takes them (as Auliyâ’), then surely he is one of them. Verily, Allâh guides not those people who are the Zâlimûn (polytheists and wrong-doers and unjust)”
If zulm (wrongdoing) is mentioned in general terms, then what is meant is major shirk and by doing that he is indicating that he agrees with the Christians in their claim that ‘Eesa (peace be upon him) was killed, but Allah, may He be glorified, has denied that in His book, where He says (interpretation of the meaning):
“but they killed him not, nor crucified him, but the resemblance of 'Īsā (Jesus) was put over another man (and they killed that man)”
Shaykh ‘Abd ar-Rahmaan al-Barraak (may Allah preserve him) said: The cross is well-known to be the idol of the Christians in their churches and in their homes, and they wear it around their necks and on their chests. Hence it is the symbol of Christianity, and it is prohibited for the Muslim to wear it.
If a Muslim wears it in order to appear to be a Christian, then this is a way of expressing his approval of the Christians in their religion, and approving of the Christians in their religion constitutes disbelief in Allah, except in the case of one who fears for his life, in which case he is regarded as being under compulsion, and Allah, may He be exalted, says (interpretation of the meaning):
“Whoever disbelieved in Allâh after his belief, except him who is forced thereto and whose heart is at rest with Faith…”
With regard to one who wears a cross out of ignorance, then he is excused because of his ignorance.
With regard to one who wears it to please the Christians, that is prohibited and there is the fear that it may come under the heading of disbelief in Allah… What the Muslim must do is beware of that which Allah has prohibited. There is no doubt that it is one of the most serious kinds of imitating the disbelievers, and the Prophet (blessings and peace of Allah be upon him) said: “Whoever imitates a people is one of them.” Narrated by Abu Dawood (4031). So what he must do is beware of that, and we ask Allah to keep us safe and sound. And Allah knows best. End quote.
Based on that, if the Muslim referred to in the question was compelled to do this, in the sense that he feared that he might be killed or imprisoned if he did not do that, then there is no blame on him in sha Allah, so long as when he did that his heart was at rest with faith.
But if the situation has not reached the point of compulsion and having no other choice, then it is not permissible for him to do that.
It is essential to differentiate between the situation of one who has been compelled to flee from his country and the situation of one who is compelled to wear a cross. He may have been compelled to flee from his country in order to escape being killed or imprisoned, but wearing a cross is not something that he is forced to do, because even if he did not wear it, he would not be subjected to killing, imprisonment and the like.
This is a matter concerning which one should be careful and understand the case of necessity in which such concessions are granted, and cases in which there is no such necessity.
Moreover, if he is patient and does not make an outward show of symbols of disbelief, or utter words of disbelief, this is better, even if he does fear for his life.
Making an outward show of symbols of disbelief in the case of necessity which makes such things permissible is a concession that is granted and there is no obligation to avail oneself of it; rather firm resolve is better than that.
With regard to fleeing for the sake of one’s religious commitment and one’s life, for fear of fitnah (persecution) or death, this is something that is prescribed in Islam and is either recommended or obligatory, according to the situation.
And Allah knows best.