The LXX rendering of Isaiah 7:14 is likely the most well-known example of how the LXX came to influence Christian discourse because it is used in Matthew 1:23 as evidence that Jesus’ birth from a virgin was foretold in Scripture. What is interesting to me is that LXX rendering of v. 15. It seems to present the child as the anti-Adam.
The language of 7:15 sounds like Genesis 2:16-17. In that passage Adam can eat (φάγῃ, v. 16) from any tree, but he cannot eat (οὐ φάγεσθε, v. 17) from the Tree of the Knowledge of Good and Evil (οῦ ξύλου τοῦ γινώσκειν καλὸν καὶ πονηρόν). In Isaiah 7:15 the child is described as eating “butter and honey” (βούτυρον καὶ μέλι φάγεται). This is a time when he is quite young. At that point, before he knows how to choose evil deliberately choose evil (πρὶν ἢ γνῶναι αὐτὸν ἢ προελέσθαι πονηρὰ) he chooses good (ἐκλέξεται τὸ ἀγαθόν).
This seems to work in the MT as well. The child will eat (יאכל) curdled milk and honey till the time he knows (לדעתו) to reject evil (ברע) and to chose good (בטוב).
This connection between eating, knowing evil, and doing good caught my attention.