Can I pray for friends to Allah, so that Allah give them mercy and clear their mind?
Is there any Qur'ānic verse in that reference?
It is perceptibly a sought-after deed to pray and wish well for your friends. Sharī'ah or universal moral code do not declare the act as prohibited rather the very teachings of the religion exhort its followers upon doing such acts of virtue. The Holy Prophet is reported to have said: The essence of the faith is to wish well for others. This means that we ought to be trying for good of our fellow human beings in all matters. It is the demand of being merely a member of the Muslim community. Generally we are more closely related with our friends and family. The basic requirements of friendship and relation entail that we should be worried about our relations as we do for ourselves. Therefore I would recommend that you should keep encouraging your friends to follow the path of righteousness and keep steadfast and pray for them.