Genesis 17:7

And I will establish my covenant between me and thee and thy seed after thee in their generations for an everlasting covenant, to be a God unto thee, and to thy seed after thee.

I will establish my covenant ... to be a God unto thee. Had this communication to Abram been made at the time of his call, it could have conveyed no other idea to the mind of one who had been an idolater, and was imbued with the prejudices engendered by idolatry, than that, instead of the ideal fictitious deities he had been accustomed to look to and worship, the true, living, personal God was to be substituted. But he had now for a long series of years become familiarized with the name, appearances, and educational training of Him who had called him, and therefore he was prepared to accept the promise in a wider and more comprehensive sense-to understand, in short, that to 'be a God unto him' included all that God had been, or had promised to be to him and his posterity-an instructor, a guide, a governor, a friend, a wise and loving father, who would confer upon them whatever was for their good, chasten them whenever they did wrong, and fit them for the high and important destiny for which he had chosen them.

It is perfectly clear that this promise was primarily meant to refer to the natural descendants of Abram, who, by the election or grace, were to be separated from the rest of the nations, and to the temporal blessings which it guaranteed to them (Romans 11:16; Romans 15:8). They were in their collective capacity to form the visible external Church; and in the sense of their being "a chosen generation, a special people," though many of them were unbelievers, they were to be called the people of God, as is manifest from the words "in their generations." In this sense partly the covenant is called an 'everlasting covenant;' for it continued in force down until the promulgation of the Gospel, when the national distinction ceased, by the admission of all mankind to the spiritual blessings contained in the Abrahamic covenant (Ephesians 2:14). But further, in a spiritual point of view, it is called "an everlasting covenant." The promise is a promise made to the Church of all ages; because He who is not the God of the dead, but of the living, made it to "Abraham, and to his seed" (cf. Galatians 3:17).

The sign of circumcision was annexed to it under the Jewish dispensation (cf. Acts 2:38-39; Galatians 3:6-7; Galatians 3:9; Galatians 3:14; Galatians 3:22; Galatians 3:26; Galatians 3:29; Hebrews 8:10), and that of baptism under the Christian dispensation. The latter denotes the very same things which were formerly symbolized by circumcision, and recognizes the same relation between parent and child (Acts 2:39, last clause). Circumcision is expressly pronounced by Paul to have been both a sign and a seal of spiritual blessings (Romans 4:11). It was a sign denoting "the putting off the body of the sins of the flesh" - i:e., denoting the necessity of the removal of the defilement of sin-the necessity of inward as well as of outward purity. It was also a seal of the covenant. It was to Abraham "a seal of the righteousness of the faith which he had, being yet uncircumcised, that he might be the father of all them that believe, though they be not circumcised, that righteousness might be imputed to them also" - i:e, not a seal of his own personal justification, but a seal of that covenant, according to the provisions of which all who should in any age believe shall be justified by faith. It was on the part of God a solemn pledge of faithfulness in the fulfillment of the promises of his covenant (Romans 3:1-2).

As observed by Abraham, therefore, as well as by all believing parents among the Jews, it was a solemn declaration of their reliance on these promises in the very act of dedicating their children to the Lord. Just as does baptism. This is one with the promise of God the Father, to make us sons "by the washing of regeneration and renewing of the Holy Ghost," through faith in the blood of God the son, "shed for the remission of sins." With this promise the sign with water is now connected, in the name of the Father, the Son, and the Holy Spirit.