This verse comes immediately after Paul's instructions to slaves in Ephesians 6:7-8: "Serve wholeheartedly, as if you were serving the Lord, not people, because you know that the Lord will reward each one for whatever good they do, whether they are slave or free."  Now he tells the slave-masters that they should treat their slaves in the same way.  It is a reminder that no boss is God and that all bosses are servants of God, whether they know it or not, whether they serve well or badly - they are accountable to Him.  

God wants every employer, foreman, manager, director, team leader or military officer to have the same wise compassion that God exercises over His 'bond-slaves'.  God is love (1 John 4:8); He is not cruel or bullying.  He does not take advantage of the weak or abuse the willing.  He does not pick favourites or decide who is on His hit-list (James 2:1).  God may work His people hard, but He rewards them generously; He may expose them to danger but always goes with them.  His training courses are always harder than we want but God never demands what He has not modelled and never stretches people beyond their ability to grow, with His help (Philippians 4:13).

Every employer is more accountable to God than to the shareholders.  He expects fairness in the workplace, compassion to those who struggle; and the growth of every skill to the maximum of everybody's ability.  God is looking to see that people are treated kindly and without favouritism (James 2:9).  He is as concerned about the managers' motivation as their methods; and He is able to measure the extent to which employers honour Him in their hearts (1 Corinthians 4:5).

So much management becomes a series of semi-automated processes, in which people can become a part of the factory workflow.  They can then become slaves to the system in which the human touch evaporates.  Wonderfully, God does not operate like that!  He treats individuals with exquisite care and yet achieves all His purposes magnificently.  He is the role model for every foreman, director and project leader.   "… do to others what you would have them do to you", is Jesus’ golden rule (Matthew 7:12).  And, not surprisingly, we cannot do that without His help!