Children of promise

Galatians 4:21-5:1
It is written that Abraham had two sons, one by a slave woman and one by a free woman.
Now Hagar is Mount Sinai in Arabia she corresponds to the present Jerusalem, for she is in slavery with her children. But the Jerusalem above is free, and she is out mother.
Now you, like Isaac, are children of promise.
We are not children of the slave but of the free woman.
For freedom Christ has set us free stand firm therefore, and do not submit again to a yoke of slavery.
Why?
Christ has set us free, but are not born from flesh but in Spirit.
Mt Sinai where the law was given to Moses
Those under the law are like the son Abraham had by his slave-woman, Hagar. But Christians are freeborn - heirs, like Isaac, to all God's promises.
How?
Let stand firm, we are born by promise, so we are free under Christ.