https://www.biblegateway.com/passage/?search=Ephesians+6%3A5-8&version=NASB

5 Slaves, be obedient to those who are your [a]masters according to the flesh, with fear and trembling, in the sincerity of your heart, as to Christ; 6 not [b]by way of [c]eye-service, as people-pleasers, but as slaves of Christ, doing the will of God from the [d]heart. 7 With goodwill [e]render service, as to the Lord, and not to people, 8 knowing that whatever good thing each one does, he will receive this back from the Lord, whether slave or free.

https://www.biblegateway.com/passage/?search=1+peter+2%3A18&version=NASB

18 Servants, be subject to your masters with all respect, not only to those who are good and gentle, but also to those who are [a]harsh.

https://www.biblegateway.com/passage/?search=Exodus+21&version=NIV

2 “If you buy a Hebrew slave, he shall serve for six years; but on the seventh he shall leave as a free man without a payment to you. 3 If he comes [a]alone, he shall leave [b]alone; if he is the husband of a wife, then his wife shall leave with him. 4 If his master gives him a wife, and she bears him sons or daughters, the wife and her children shall belong to her master, and he shall leave [c]alone. 5 But if the slave plainly says, ‘I love my master, my wife, and my children; I will not leave as a free man,’ 6 then his master shall bring him to [d]God, then he shall bring him to the door or the doorpost. And his master shall pierce his ear with an [e]awl; and he shall serve him permanently.