To make covenant with God, is impossible, but by mediation of such as God speaketh to, either by revelation supernatural, or by His lieutenants that govern under Him, and in His name: for otherwise we know not whether our covenants be accepted, or not. And therefore they that vow anything contrary to any law of Nature, vow in vain; as being a thing unjust to pay such vow. And if it be a thing commanded by the law of Nature, it is not the vow, but the law that binds them.

The matter, or subject of a covenant, is always something that falleth under deliberation; for to covenant is an act of the will; that is to say, an act, and the last act of deliberation; and is therefore always understood to be something to come; and which is judged possible for him that covenanteth to perform.

And therefore, to promise that which is known to be impossible, is no covenant. But if that prove impossible afterwards, which before was thought possible, the covenant is valid, and bindeth, though not to the thing itself, yet to the value; or, if that also be impossible, to the unfeigned endeavour of performing as much as is possible: for to more no man can be obliged.