48 And when a stranger shall sojourn with thee, and will keep the passover to the Lord, let all his males be circumcised, and then let him come near and keep it; and he shall be as one that is born in the land: for no uncircumcised person shall eat thereof. 49 One law shall be to him that is homeborn, and unto the stranger that sojourneth among you.
In these verses we have the first instances of God providing a path for a any person, even one who was not a direct descendant of Abraham, to become a part of His covenant people. Previously, God had chosen specific individuals to extend His promises to. Isaac was chosen and not Ishmael, Jacob and not Esau. Now, though, any outsider could enter into the fold of God through the sign of being circumcised. Then they would be “as one that is born in the land.”
“As one that is born in the land” means to receive the same rights, privileges, and covenants that chosen people enjoyed. They would receive the same promises that God had given to Abraham, with all of its accompanying blessings, both in this life and the next, culminating in the promise of eternal salvation. This was the most generous and hopeful gift imaginable, a path to salvation for all, an opening of the doors that Jesus would expand further many years later.
But it was, of course, necessary for the outsider to sincerely take on the Hebrew covenants and obligations to receive these promises. Too often it is argued that since the gospel is freely offered to all people that it cannot then have any requirements of those people. But the thing that is being freely offered is a law, while obtaining the positive outcomes of that law depend on it being followed. The gift from God is the opportunity to first accept His terms and then receive His rewards.
God reinforces this in verse 49 when He says “one law…to him that is homeborn, and unto the stranger that sojourneth among you.” One law, but God has described two different outcomes: one where a person becomes a part of the covenant through circumcision and one where a person remains a outsider by declining God’s offer. God is not contradicting Himself by stating “one law,” but with two outcomes, as every law necessarily separates people into different categories. Having a legal age limit to drive, for example, is just one law, but it dictates two outcomes depending on a citizen’s age. So, too, God’s law is freely given to all, but that doesn’t mean that the positive side of it is in force for all, only for those who meet the terms for it. That is still a gift, though, because it is a path for us to claim God’s greatest blessings, where otherwise we would not have any means to do that.