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.
KJV:
He therefore that despiseth, despiseth not man, but God, who hath also given unto us his holy Spirit.
NASB:
So, he who rejects this is not rejecting man but the God who gives His Holy Spirit to you.
KJV:
Having damnation, because they have cast off their first faith.
NASB:
thus incurring condemnation, because they have set aside their previous pledge.