Paul continues his discussion explaining that the promise preceded the Law (Abraham called 430 years before Sinai) and therefore being children of the promise outranks keeping the law. He continues by noting that the law was a guardian, put in place like a Parental Guardian to keep us in check until we could enter our inheritance. It is an interesting argument, again, one that does not move us much in the modern world. What follows does:
We are children of God: Adopted sons and daughters. When we became members of the body of Christ through our baptism we "put on Christ" like a suit of clothing and entered a whole new way of living. Here is the best part: in Christ ALL differences are to disappear. See verse 28: in Christ there is neither Jew nor Greek, Slave nor Free, Male nor Female: we are all one in Christ. The human divisions of religion (Jew or Greek) race (Jew or Greek) economic status (slave or free) or gender (male or female) are eliminated when we put on Christ. In Christ all human distinctions or power and status and wealth are invalid and we stand as one in Christ. The distinctions in the church are not to be about the human distinctions but only the distinctions of role and function (many gifts one spirit).
In many church traditions this is evidenced at funerals. The Church provides a cloth -- usually embroidered with the symbols of the Christian faith -- that is placed over a casket. This cloth is called a pall (hence the phrase "pall bearers"). The pall was placed over the casket so that the quality and workmanship of the casket would not be on display in the sanctuary. The church did this as a reminder that in Christ the older distinctions of race, status and gender do not have a place. In Christ we are all one.