Galatians 4:23-25

4:23 But one, the son by the slave woman, was born by natural descent, ¹  while the other, the son by the free woman, was born through the promise. 4:24 These things may be treated as an allegory, ²  for these women represent two covenants. One is from Mount Sinai bearing children for slavery; this is Hagar. 4:25 Now Hagar represents Mount Sinai in Arabia and corresponds to the present Jerusalem, for she is in slavery with her children.

[4:23]  ¹ tn Grk “born according to the flesh”; BDAG 916 s.v. σάρξ 4 has “Of natural descent τὰ τέκνα τῆς σαρκός children by natural descent Ro 9:8 (opp. τὰ τέκνα τῆς ἐπαγγελίας). ὁ μὲν ἐκ τῆς παιδίσκης κατὰ σάρκα γεγέννηται Gal 4:23; cp. vs. 29.”

[4:24]  ² tn Grk “which things are spoken about allegorically.” Paul is not saying the OT account is an allegory, but rather that he is constructing an allegory based on the OT account.