At the Last Supper Jesus bid all His disciples to drink from the third cup, the cup of redemption, saying “For this is my blood of the covenant which is poured out for many for the forgiveness of sins.” Recall that a covenant and a will or testament are closely related, with the same Greek word used for both, and it is from the words Jesus used here at the Last Supper that we obtain the names of the two great divisions of our Bible. How exactly are a will and a covenant related, and what is the relationship between the inheritance of a will or testament, and the blessings and promises of a covenant? Notice that although there are differences depending upon the context, the underlying significance of both that connects them is their inviolableness because of a death that has taken place. A covenant is in force between the living who have “cut” a covenant symbolizing their own deaths so that it becomes inviolable and cannot be changed; cf. Gal 3:15. Similarly, a will is in force only when the one who made it has died so that it too cannot be changed. An inheritance is simply the outcome of the disposition of the terms of the will that has been enacted by the death of the one who made it. Likewise, the blessings and promises of the covenant are the outcome of the disposition of the terms of the covenant that have been enacted by the two parties.
Notice that since God cannot literally die as men do, any testament or will from God that bequeaths to us a blessing is necessarily more along the lines of a covenant that is inviolable, having been sworn to by Himself as the highest form of assurance He could give to man; cf. Heb 6:13-18. When God enters into a covenant by agreeing to do something or swears by Himself with an oath (cf. Gen 22:16, Isa 45:23, etc…), because of His nature that cannot change, it is similar to when a person dies after signing a will, which cannot then be changed.
As the Son of God, did Jesus have something willed or covenanted to Him by the Father? See Mat 21:38. What was His inheritance from the Father? See Psa 2:8, Eph 1:18. In what way did the unbelieving Jews want to seize Jesus’ inheritance of the Gentile nations that He would set free from the bondage of sin and rule over in righteousness? Think: what did the unbelieving Jews want their relationship to be to the Gentile nations, and how did that affect their understanding of the Messiah? Just as Jesus as the only begotten Son of the Father inherited from Him a kingdom over all the nations of the world, what do those who stand by Him and partake of the New Testament in His blood inherit as a result of His death? See Luk 22:29 and notice that the NAS grant (KJV appoint, ESV assign, NIV confer on) is the verbal form of covenant or will; i.e., literally, “And I covenant / will to you, just as my Father covenanted / willed to me, a kingdom”. See also Isa 42:6-7, 49:1-10; cf. Mat 25:32-34, Act 26:16-18, Eph 1:10-14, Col 1:12-14. Whereas God used the earthly kingdom of Israel as a tangible object lesson to the Jews, in what way was an inheritance in that kingdom only a shadow of the inheritance in the kingdom of God that He wills to those who partake of the New Testament in His blood? See Mat 19:29, Heb 9:13-15, 1Pe 1:3-4, Rev 21:1-7.
Notice also that as with the blessings of a covenant, the inheritance of a will is contingent upon the fulfillment of its terms. An inheritance is something received from another, often a father, that was the product of his labor, something that he earned or started that is then passed on, most often to his children, to build upon; cf. Isa 5:1-7. In addition to specifying an heir, a will may also provide a directive of the father’s wishes of what the children or other beneficiaries must do in order to receive the inheritance, and may include stipulations for how the inheritance is to be used. In a loving, established relationship, such stipulations are not necessarily articulated, but what is willed is still typically done so with the implication that it will be used or managed by the one inheriting it in accordance with the will or wishes of the one who made it. In what way is this also true of Christ’s kingdom willed to us through Him for an inheritance? See Act 20:32, 1Co 6:9-10, 15:50, Gal 5:19-21, Eph 5:5, 1Pe 3:9.
 Ancient peoples understood the corporate value of being faithful to their words and considered such unchangeableness much more highly and sacred than we do today. This value is reflected in the laws of the Medes and the Persians that could not even be changed by the king once enacted; cf. Est 1:19, 3:9, 8:5-8,10-11, Dan 6:8,12,15.