Antisemitism, page-1221

“It is forbidden to inform about a colleague to the gentiles and endanger his physical person or his property.

This applies even when the person concerned is a wicked person who commits sins, and even if he causes one irritation and discomfort.

Anyone who actually informs about a jew and endangers his person or his property to the gentiles will not receive a portion in the world to come.

It is permissible to kill a moseir (snitches end up in ditches) in any country, even in the present age, when the court no longer metes out capital punishment.

It is permitted to kill him before he informs. When he says: "I will inform on so and so and endanger his person and/or…”