Praise be to Allah.
There is nothing wrong with the Muslim learning foreign languages. Indeed, that may be required and rewarded, if one learns their language in order to call them to Islam and strives to guide them to the truth from which they have gone astray, or if one intends to benefit from the knowledge that they have that the Muslims do not have, so that he will be able to benefit the Muslim by means of this knowledge.
But we think that the way that you have mentioned is not permissible, and we think that these people are deceiving the Muslims in order to divert them from their religion. This class is not a language learning class; rather it is a class in Christianity.
We Muslims believe that the Bible has been distorted and tampered with by Christian scholars, and it now contains falsehoods and myths that no one with a sound mind can believe.
Reading these distorted books is not permissible, except for one who has enough Islamic knowledge to be able to distinguish between truth and falsehood in them, and who reads them with the aim of refuting their followers and convincing them that what is in these books is falsehood.
Hence the Prophet (peace and blessings of Allah be upon him) got angry when he saw a book in the hand of ‘Umar ibn al-Khattab (may Allah be pleased with him) that he had taken from some of the People of the Book. The Prophet (peace and blessings of Allah be upon him) said: “Are you in doubt of it, O son of al-Khattab? By the One in Whose hand is my soul, I have brought to you that which is white and pure, and by the One in Whose hand is my soul, if Musa ((peace be upon him) were alive, he could do nothing but follow me.” [Imam Ahmad].
Allah has told us that these people are plotting and that they will do all that they can to take the Muslims away from their religion. Allah says (interpretation of the meaning): “And they will never cease fighting you until they turn you back from your religion (Islamic Monotheism) if they can.” [2:217]
Shaykh al-S’adi (may Allah have mercy on him) said:
Allah tells us that they will never stop fighting the believers, and that their aim is not to steal their wealth or kill them; rather their aim is to turn them back from their religion so that they will become disbelievers after having believed, and so that they will be doomed to Hell. So they are doing all that they can to achieve this and striving as hard as they can, but Allah will not allow except that His Light should be perfected even though the Kafirun (disbelievers) hate (it) [9:32].
This description is general and applies to all the disbelievers. They will not cease to fight others until they turn them back from their religion, especially the People of the Book, the Jews and Christians, who set up organizations and send missionaries and doctors, and build schools in order to attract people to their religion and to introduce to them whatever they can of specious arguments which will make them doubt their religion.
But hope comes from Allah Who has blessed the believers with Islam and has chosen for them His true religion, and has perfected His religion for them, and has completed His blessings upon them, and has thwarted everyone who wants to extinguish His light, caused their plans to fail, supported His religion and made His word supreme.
This verse speaks the truth about these disbelievers as it speaks the truth about those who came before them (interpretation of the meaning): “Verily, those who disbelieve spend their wealth to hinder (men) from the path of Allah, and so will they continue to spend it; but in the end it will become an anguish for them. Then they will be overcome. And those who disbelieve will be gathered unto Hell.” [8:36] End quote. Tafsir al-S’adi.
What you have to do is prevent your wife from going to these people and not go along with them and their evil plots. It is essential to warn every Muslim man and woman who may be deceived by such people, and expose their plots and schemes.
It is possible to learn English by many easy ways that do not involve any problems, missing of issues or misguidance.
We ask Allah to thwart the plot of these people and to give the Muslims insight into their plots.