I want to say this to start I am not a dispensationalist, I do not claim to be anything but a Christian, I go to a Reformed Church. With that said lets look it what the Bible says.
Here is the problem with the OP Galatians 4:24 “Now this may be interpreted allegorically: these women are two covenants. One is from Mount Sinai, bearing children for slavery; she is Hagar.”
It does not say theologially. Here's what BAGD says about the Greek word used, calling it "mythical" so Paul did not mean it literally, he says this maybe interpreted allegorically, again not literally or theologically.
The literal words seen, convey a spiritual meaning ....not seen . We compare the spiritual not seen to the same called "faith to faith as it is written . The literal words the letter of the law kill. The spiritual understanding heals.
Calling it "mythical" as if it remains a mystery does not dismiss the theological responsibility of rightly dividing what it infallibly informs us.
The prescriptions for rightly dividing must be theologically applied. Without parables the allegorical teaching, the spiritual understanding is hid. Christ, the word of God spoke not without parables.
Without the prescription for rightly dividing parables found in 2 Corinthians 4:18 men would have no idea what it means that the church is the mother of us all. It certainly has nothing to do with the outward flesh of a Jew or a gentile. That’s a man distinction which disappears in the parables.
2Co 4:18 While we look not at the things which “are seen”, but at the things which “are not seen”: for the things which are seen are temporal; but the things which are not seen are eternal.
Paraphrased it would read.. While we look not at the things which are seen,
the flesh of a Jew or a Gentile , but at the things which are not seen: for the things which are seen
flesh and blood are temporal; but the things which are not seen
are eternal,
the new promised incorruptible bodies
Failure to distinguish between the things
seen of man from the things
not seen of God, clearly offends God who is not a man as us and remains not seen .
That can be seen when Peter blasphemes the Holy name by which we are called heavenward. Acting as a dynamic duel (God said unto
Peter, Get thee behind me,
Satan ) as one of the many antichrists that were there at that time period as an example this helps us define how the spirit of the antichrist (Satan) works to prevent the gospel from going out.
(Purple in parenthesis) my personal comments.
Then Peter took him, and began to rebuke him, saying, Be it far from thee, Lord: this shall not be unto thee.But he turned, and said unto Peter, Get thee behind me, Satan: thou art an offence unto me: for thou savourest not the (unseen) things that be of God, but those (seen) that be of men. Mat 16:22