Hi
Enlightenedtruth
That opens a different can of worms; why would God want men to alter the "natural body" that He gave them. Does that apply to Matthew 1:21 in saving his people from Sin?
Perhaps I might be able to shed some light on this matter for you.
God made a promise to a man named Abram. Now, before you ask, nobody can really tell you why God chose Abram. I'm guessing that as God, He knew Abram's nature and that he would see through the work that God had for him. But I can't, with any real assurance say that's why God picked Abram.
But God made a promise to him that He was going to raise up a nation to honor and follow Him as a nation of people. Now, for your gentile question, everyone not born of the line of Abraham, through Isaac and then later through the men who became the heads of the 12 tribes of Israel, is a gentile. The sons of Ishmeal were gentiles. Only the sons of the promise that God's word tells us of, became Israel.
Anyway, God made this promise to Abram and acted through him to raise up this nation of people to be His people. As a part of that, He made another covenant with Abram and told him that all males had to be circumcised as a sign of their belonging to Him. It was a sign. Just as the dietary restrictions are a sign.
The dietary laws are signs that kept the nation of Israel separated from the people of the other nations of the world. Still today, devout Jews are loath to eat with gentiles. So, the covenant of circumcision and the condemnation of certain foods for the people of Israel, was, as I understand it how God knew that He could keep His people apart. Even in Egypt we read that the Israelites would not eat with the Egyptians because their foods were often not in keeping with their dietary restrictions that God had placed on them. Same thing happened in Babylon. Of course, we also know that the Egyptians didn't want to eat with the Hebrews because they considered them a very unclean and despicable people. So, these restrictions that God placed on His people under the old covenant were, for the most part, and not including the 10 commandment law, merely to insure that they had a difficult time assimilating into the other nations.
But you might want to up your study game of the Scriptures. God gives Abram the reason for the covenant of circumcision.
This is my covenant with you and your descendants after you, the covenant you are to keep: Every male among you shall be circumcised. You are to undergo circumcision, and it will be the sign of the covenant between me and you.
For the generations to come every male among you who is eight days old must be circumcised, including those born in your household or bought with money from a foreigner—those who are not your offspring. Whether born in your household or bought with your money, they must be circumcised. My covenant in your flesh is to be an everlasting covenant. Any uncircumcised male, who has not been circumcised in the flesh, will be cut off from his people; he has broken my covenant.” Genesis 17:10-14.
Hope that helps.
God bless,
Ted