'Bond servant' in the Bible

Jesus answered them, Truly, truly do I say to you, Every one that committeth sin is a bondservant of sin.

And the bondservant abideth not in the house for ever; the son abideth for ever.

Now I say, that the heir, as long as he is a child, differeth in no respect from a bondservant, though he is lord of all;

So then thou art no longer a bondservant, but a son; and if a son, then an heir through God.

no longer as a bondservant, but above a bondservant, a brother beloved, especially to me, but how much more to thee, both in the flesh, and in the Lord!