For ever, i.e. all the time of his life, or, at least, till the year of jubilee. See on Exo_21:6.
Unto thy maid-servant thou shalt do likewise, i.e. either dismiss her honourably, and with plenty of provisions; or engage her to perpetual servitude in the same manner, and by the same rites; whence it appears that this case differs from that Exo_21:7, and that the maid-servant there was taken in upon other and better terms than this here.