Praise be to Allaah.
It is not permissible to hand over Islamic works such as those mentioned to kaafir workers, because they cannot be trusted and we cannot be sure that they are sincere. Allaah says (interpretation of the meaning);
“Indeed there has been an excellent example for you in Ibraaheem (Abraham) and those with him, when they said to their people: ‘Verily, we are free from you and whatever you worship besides Allaah, we have rejected you, and there has started between us and you, hostility and hatred for ever until you believe in Allaah Alone’” [al-Mumtahanah 60:4]
“The believers, men and women, are Awliyaa’ (helpers, supporters, friends, protectors) of one another” [al-Tawbah 9:71]
“And those who disbelieve are allies of one another, (and) if you (Muslims of the whole world collectively) do not do so [i.e. become allies, as one united block under one Khaleefah (a chief Muslim ruler for the whole Muslim world) to make victorious Allaah’s religion of Islâmic Monotheism], there will be Fitnah (wars, battles, polytheism) and oppression on the earth, and a great mischief and corruption (appearance of polytheism)”
The Council of Major Scholars in the Kingdom of Saudi Arabia has issued a statement that it is forbidden to delegate the building of mosques to non-Muslims, because of the evidence (daleel) and reasons referred to above.