I would have the Reader attend to the expressions in these verses, with an eye to the original covenant of grace, and he will then enter into a proper apprehension of them. That original covenant was, that in the seed of Abraham, should all the nations of the earth be blessed. "He saith not (saith the apostle Paid) and to seeds, as of many, but as of one, and to thy seed, which is CHRIST." Galatians 3:16. When GOD, therefore, is here said to avouch himself to be the LORD GOD of Israel, it is that in CHRIST, GOD promiseth to bless his people, and to accept them in him. And his people avouch GOD to be their GOD in CHRIST; depending upon the fulfillment of all his promised covenanted mercies in him. Those expressions of making Israel high, in name, in honour, and in praise; and an holy people above all nations, are all very striking characters of the Israel of GOD. And who is, or ought to be, so holy, so high, so honourable, in their birth, their state; their life, their conversation, as those who have fellowship with the FATHER, and with his Son JESUS CHRIST? Who so peculiar as those, whom the LORD GOD of heaven and earth hath made his Segullah, that is, his chosen ones, his peculiar people. Reader! may it be your happiness and mine, to do as Israel did, avouch GOD to be our GOD, and may he avouch us to be his people.
Deuteronomy 26:16-19
16 This day the LORD thy God hath commanded thee to do these statutes and judgments: thou shalt therefore keep and do them with all thine heart, and with all thy soul.
17 Thou hast avouched the LORD this day to be thy God, and to walk in his ways, and to keep his statutes, and his commandments, and his judgments, and to hearken unto his voice:
18 And the LORD hath avouched thee this day to be his peculiar people, as he hath promised thee, and that thou shouldest keep all his commandments;
19 And to make thee high above all nations which he hath made, in praise, and in name, and in honour; and that thou mayest be an holy people unto the LORD thy God, as he hath spoken.