Ephesians 6:5

6:5 Slaves, obey your human masters with fear and trembling, in the sincerity of your heart as to Christ,

Colossians 3:22-23

3:22 Slaves, obey your earthly masters in every respect, not only when they are watching – like those who are strictly people-pleasers – but with a sincere heart, fearing the Lord. 3:23 Whatever you are doing, work at it with enthusiasm, as to the Lord and not for people,