and constitution, things of so much certainty and assurance, that
by way of excellency, a covenant is called, a sure one, or an assurance.
When a sure one is but named, a covenant must be understood. As, the
"Holy One" is God, and the "Holy One and the Just," is Christ. You may
know whom the Holy Ghost means, when He saith "The Holy One and the
Just." So the sure one, is a covenant. You may know what they made, when
the Holy Ghost saith, they made a sure one. Hence observe, that

A well grounded covenant is a sure, a firm, and an irrevocable act. When
you have such an _all this_, (and such you have) as is here concentrated
in the text, to lay into, or for the foundation of a covenant, the
superstruction is _aeternitati sacrum_, and must stand for ever.

A weak ground is but a weak obligation; and a sinful ground is no
obligation. There is much sin in making a covenant upon sinful grounds,
and there is more sin in keeping of it. But when the preservation of
true religion, and the vindication of just liberties meet in the
groundwork, ye may swear and not repent; yea, if ye swear, ye must not
repent. For because of all such things as these, we ought (if we make
any, and that we ought) to make a sure covenant.

The covenant God makes with man is a sure covenant. Hence called a
"Covenant of salt," because salt preserves from perishing and
putrefaction. The covenant of God with man about temporal things, is
called a "Covenant of Salt, and a covenant forever." For tho' His
covenant about temporal things (as all temporals must) hath an end of
termination, yet it hath no end of corruption: time will conclude it,
but time cannot violate it. But as for His covenant about eternal
things, that, like eternity, knows not only no end of corruption, but
none of termination. "Altho' my house (saith gasping David) be not so
with God; yet He hath made with me an everlasting covenant, ordered in
all things and sure: for this is all my salvation, and all my desire,
altho' He make it not to grow." And what is it that makes the covenant
of God with man thus sure? sure not only in itself, but (as the apostle
speaks) to all the seed. Is it not this, because it hath a strong
foundation, a double, impregnable foundation? _First_, His own free
grace. _Second_, The blood of Christ; which is therefore also called,
the blood of the covenant. Because of all this, this all, which hath an
infinity in it, the Lord God hath made with us a sure covenant.