two of my best muslim friends do not talk to each other. please let me know what kind of sin they are commeting. secondly, if they pray side by side will it affect the prayers of others (since they do not have relationship between them)

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

Islam does not allow Muslims to break their relation or to desert each other except for Islamicly valid reasons as we have mentioned in Fataawa 86772 and 86090.

However, their prayer is valid and if they stand together in the prayer it does not affect other people's prayers.

Allaah Knows best.