KJV:
Wherefore I beseech you that ye would confirm your love toward him.
NASB:
Wherefore I urge you to reaffirm your love for him.
KJV:
Brethren, I speak after the manner of men; Though it be but a man's covenant, yet if it be confirmed, no man disannulleth, or addeth thereto.
NASB:
Brethren, I speak in terms of human relations: even though it is only a man's covenant, yet when it has been ratified, no one sets it aside or adds conditions to it.