The ESV renders it:
Jas 5:16 Therefore, confess your sins to one another and pray for one another, that you may be healed. The prayer of a righteous person has great power as it is working.
The KJV renders it:
Jas 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.
When the words "effective" and "fervent" are taken out of the ESV passage it does in fact change the verse and its meaning. It takes out the manner in which prayer was to be done.
Was this appropriate? How do we know?
Jas 5:16 Therefore, confess your sins to one another and pray for one another, that you may be healed. The prayer of a righteous person has great power as it is working.
The KJV renders it:
Jas 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.
When the words "effective" and "fervent" are taken out of the ESV passage it does in fact change the verse and its meaning. It takes out the manner in which prayer was to be done.
Was this appropriate? How do we know?