Prayer is a very powerful thing in the hands of a righteous man. It can change events. God will listen to a request and grant it if the person is righteous. James says in chapter 5:16,
"Confess your faults one to another, and pray one for another, that ye may be healed. The effectual fervent prayer of a righteous man availeth much."
or as the RSV says,
“The prayer of a righteous man has great power in its effects.”