'My Covenant' in the Bible

For so says Jehovah to the eunuchs who keep My Sabbath, and choose things that please Me, and take hold of My covenant;

Also the sons of the stranger, who join themselves to Jehovah to serve Him, and to love the name of Jehovah, to be His servants, everyone who keeps from defiling the Sabbath, and takes hold of My covenant;

As for Me, this is My covenant with them, says Jehovah; My Spirit that is on you, and My Words which I have put in your mouth, shall not depart out of your mouth, nor out of the mouth of your seed, nor out of the mouth of your seed's seed, says Jehovah, from now on and forever.