The Scripture sense of this word is the same as in the circumstances of common life; namely, an agreement between parties. Thus Abraham and Abimelech entered into covenant at Beersheba. (Genesis 21:32) And in like manner, David and Jonathan. (1 Samuel 20:42) To the same amount, in point of explanation, must we accept what is related in Scripture of God's covenant concerning redemption, made between the sacred persons of the GODHEAD, when the holy undivided Three in One engaged to, and with, each other, for the salvation of the church of God in Christ. This is that everlasting covenant which was entered into, and formed in the council of peace before the word began. For so the apostle was commissioned by the Holy Ghost, to inform the church concerning that eternal life which was given us, he saith, in Christ Jesus, "before the world began?" (Titus 1:2; 2 Timothy 1:9) So that this everlasting covenant becomes the bottom and foundation in JEHOVAH'S appointment, and security of all grace and mercy for the church here, and of all glory and happiness hereafter, through the alone person, work, blood-shedding, and obedience of the Lord Jesus Christ. It is on this account that his church is chosen in Christ before the foundation of the world. (Ephesians 1:4) And from this appointment, before all worlds, result all the after mercies in time, by which the happy partakers of such unspeakable grace and mercy are regenerated, called, adopted, made willing in the day of God's power, and are justified, sanctified, and, at length, fully glorified, to the praise of JEHOVAH'S grace, who hath made them accepted in the Beloved.
Such are the outlines of this blessed covenant. And which hath all properties contained in it to make it blessed. It is, therefore, very properly called in Scripture everlasting; for it is sure, unchangeable, and liable to no possibility of error or misapplication. Hence, the patriarch David, with his dying breath, amidst all the untoward circumstances which took place in himself and his family, took refuge and consolation in this: "Although (said he,) my house be not so with God, yet hath he made with me an everlasting covenant, ordered in all things, and sure; for this is all my salvation and all my desire, although he make it not to grow." (2 Samuel 23:5)
In the gospel, it is called the New Testament, or covenant, not in respect to any thing new in it or from any change or alteration in its substance or design, but from the promises of the great things engaged for in the Old Testament dispensation being now newly confirmed and finished. And as the glorious person by whom the whole conditions of the covenant on the part of man was to be performed, had now, according to the original settlements made in eternity, been manifested, and agreeably to the very period proposed, "in [what is called] the fulness of time, appeared to put away sin by the sacrifice of himself," it was, therefore, called Covenant, in his blood. But the whole purport, plan, design and grace, originating as it did in the purposes of JEHOVAH from all eternity, had all the properties in it of an everlasting covenant; and Christ always, and from all eternity, "was considered the Lamb slain from the foundation of the world." (Revelation 13:8)