When the Bible speaks of God's promises, it is important to recognize both the nature of the promise as well as how the promise functions. One must understand God's motivation for His promise, the method by which He will keep the promise, and the conditions that enable one to receive the benefits of His promises. For example, in Genesis chapter 12, God promised Abraham that he would be a great nation, would receive a great land inheritance, and that his descendant would be a blessing to all of the families of the world. The scriptures do not state any conditions placed upon Abraham. In fact, in Genesis chapter 15, God confirmed and ratified His promises with Abraham and did so without the participation of Abraham to show that such promises were unconditional. God would not rely on Abraham in any way, shape or form to fulfill those promises.
Later in Genesis chapter 17, God re-confirmed His promises to Abraham. Though Abraham had been living in a state of unrepentant sin and disconnection from God for 14 years, God reached out to Abraham and sought to remind Abraham about His promises, as well as the magnitude of the promises and His being. Upon calling Abraham to repent, the Lord drilled the point down that He would fulfill His promises on His own in spite of the flaws of Abraham. The Abrahamic Covenant is purely unconditional. There is nothing that Abraham was instructed to do in order to cause God to fulfill these promises. Whether Abraham did right or wrong, God was going to do what He said. However, Genesis 17:9-14 does express that God had an expectation in regards to who would receive the benefits of God's promises.
Genesis 17:9-14 outlines the Jewish covenant of circumcision. In this portion of scripture, God commanded that Abraham and all of his descendants should be circumcised. God commanded that the covenant of circumcision should be an everlasting covenant, meaning that every descendant until the end of time is to practice the process of circumcision. God commanded that Abraham and his offspring must have the "foreskin of his flesh" cut off. Every male child relative of Abraham was to be circumcised on the 8th day. God also made it so that if foreigners or slaves were living in the households of Jews and had babies in the homes of Jewish people, they too were to be circumcised in the same manner.
The Book of Romans states that God's real emphasis in the commandment of circumcision was symbolic of a greater spiritual work that God desired. The cutting off of flesh on the 8th day was to be a symbol or picture of one cutting away the desires of one's flesh on the day of new beginnings. The 8th day in Biblical contexts symbolizes new beginnings since it is the start of a new week. In the context of circumcision, it is a picture of regeneration by being "born again" of the Spirit through faith in Jesus Christ. Therefore, since one is born again, one is expected to walk in the Spirit of God instead of by the corruption of one's flesh. The purpose in being born again is so that the conscience of a person experiences a transformation. The Bible teaches that the Spirit of God will dwell within the hearts of those who are humbly repentant and seek the Lord Jesus in faith. Upon dwelling in the heart of a believer, the Bible teaches that the Spirit of God will begin to work to change the conscience of a person so that the believer will have strong desires and urges to obey God and be righteous according to His standards as dictated in the Word. Consequently, one will gradually aspire less to follow the fleshly and worldly affections that one naturally has to please one's own flesh in ways that are contrary to the will of God. The physical act of circumcision is supposed to be a picture of the "cutting away" of one's flesh that the Holy Spirit does in salvation in order that one is identified by God rather than one's flesh. One then becomes an heir to the promises of God as one is obedient to the command of God within the unconditional covenant of God and thereby identified in God.
This principal explains a very important point in regards to the promises of God and how they relate to people. God's promises are unconditional. Whether Abraham obeyed the command of circumcision or not, God was going to fulfill His promises to make Abraham a great nation, give him the land, and bring about the blessing. No matter what, God was going to do those things. However, Genesis 17:9-14 is explicit to mention that those who disobey the commands of circumcision were to be cut off from his people. One that is cut off from the lineage of Abraham would represent one that is disqualified from receiving the promises of Abraham. God would still fulfill the promises, but the command of circumcision revealed one's individual accountability and responsibility to trust in God through obedience in order to receive the benefits of God's work. God would provide a great nation, a land inheritance, and a blessing. However, only those who trusted in God's Word through obedience would be those who became beneficiaries of those promises and were able to be a part of the great nation, dwelling in the land, and partaking of the blessing.
The Bible is clear to show that God's promises are unconditional and nature and big enough so that anyone who wants to partake in the benefits of those promises may do so. Jesus said that whoever desires to drink the water of life may go to Him and drink freely. The promise of water is unconditional. One must simply submit to the manner of provision that God instructs and go to Jesus to drink it. The promises in the Abrahamic Covenant and eternal life (which is a part of that covenant through the blessing) is unconditional and God is working to fulfill it to completion. The benefits of those promises are available to everyone - not just Jews. The promises will be fulfilled. If one desires to be an heir of those promises, one can freely do so if one is willing to abide by the methods of provision that God commands.
Romans 2:29 clarifies that the issue of literal circumcision is not the manner by which one is considered a Jew, an heir of Abraham, or an heir of the Abrahamic Covenant. God is concerned with the circumcision of the heart. God desires that one cut away the wicked desires and motives of one's flesh that disconnect people from God's presence. God desires that His children stop living in selfish and prideful sin that separates from God. Its as if an invitation went out to the world that a rich man was willing to pay off the debt of every single person who came to him on a certain day. The man would pay the debt of anyone who came so that all one has to do is show up and one's debt is paid. There is no condition, one just has to show up. There are benefits to be taken advantage of, but one must simply show up in order to do so. In a similar manner, God is willing to forgive sins and allow one to partake in all of the eternal benefits of His promises, so long as one simply shows up. However, the manner in which God demands that one show up in His presence is in humility and in repentance. God cannot look upon sin, so God simply asks that one come to Him with the heart to live apart from sin. Since God's promises are unconditional, when one approaches God in humility and repentance, He takes care of the rest so long as one remains humble and repentant. It is then, and only then that one can become a beneficiary of the greatest promises ever known to mankind!