'My Covenant' in the Bible

For the mountains may depart, and the hills be removed; but my lovingkindness shall not depart from thee, neither shall my covenant of peace be removed, saith Jehovah that hath mercy on thee.

For thus saith Jehovah of the eunuchs that keep my sabbaths, and choose the things that please me, and hold fast my covenant:

Also the foreigners that join themselves to Jehovah, to minister unto him, and to love the name of Jehovah, to be his servants, every one that keepeth the sabbath from profaning it, and holdeth fast my covenant;

And as for me, this is my covenant with them, saith Jehovah: my Spirit that is upon thee, and my words which I have put in thy mouth, shall not depart out of thy mouth, nor out of the mouth of thy seed, nor out of the mouth of thy seed's seed, saith Jehovah, from henceforth and for ever.