and the certain product of all the mercy promised in it might, were that our present task, be easily demonstrated; as,— First, From the removal of all causes of alteration. When two enter into covenant and agreement, no one can undertake that that covenant shall be firm and stable if it equally depend upon both; yea both, it may be, are changeable, and so actually changed before the accomplishing of the thing engaged about therein: however, though the one should be faithful, yet the other may fail,