What is the ruling of Islam concerning a missionary group adopting Muslim orphans, and what is the evidence for it?

It is not permissible to hand over Muslim orphans to disbelievers, such as Christians, due to the great danger this poses to their Islamic upbringing, and because they are a trust in the hands of Muslims. Allah Almighty said: "And the believing men and believing women are allies of one another," and He said: "And those who disbelieved are allies of one another. If you do not do so, there will be tribulation on earth and great corruption."