'Master' in the Bible

You masters, do the same [showing goodwill] toward them, and give up threatening and abusive words, knowing that [He who is] both their true Master and yours is in heaven, and that there is no partiality with Him [regardless of one’s earthly status].

For our struggle is not against flesh and blood [contending only with physical opponents], but against the rulers, against the powers, against the world forces of this [present] darkness, against the spiritual forces of wickedness in the heavenly (supernatural) places.