Note that this first group of workers wanted a definite contract with the householder before they would work. The later groups were willing to work simply by faith in the employer's word that "whatsoever is right I will give you" (Matthew 20:4), and he rewarded their faith abundantly. Even those hired at the eleventh hour received the same wages, for they would have been willing to work all day (Matthew 20:7) if they had known. Thus, rewards for Christian service are based more on motive and opportunity than on quantity (1 Corinthians 3:13-15).

Source:

KJV Defenders Study Bible, by Dr. Henry Morris, Ph.D.
Publisher: Thomas Nelson
Language: English
DEF 10 ISBN 0-529-10444-x
DEF 10-1 ISBN 0-529-10445-8