Isaiah 7:14
13 So Isaiah replied, “Pay attention, family of David. Do you consider it too insignificant to try the patience of men? Is that why you are also trying the patience of my God? 14 For this reason the Lord himself will give you a confirming sign. Look, this young woman is pregnant and will give birth to a son. You, young woman, will name him Immanuel. 15 He will eat sour milk and honey, which will help him know how to reject evil and choose what is right.
LXX Isaiah 7:14
13 Then he said: “Hear now, O house of Dauid! Is it a small thing for you to provoke a fight with mortals? How then do you provoke a fight with the Lord? 14 Therefore the Lord himself will give you a sign. Look, the virgin shall be with child and bear a son, and you shall name him Emmanouel. 15 He shall eat butter and honey; before he knows or prefers evil things, he shall choose what is good.
Notes and References
"... Besides the translator's insertion of καί in Isaiah 7:16 and ἀλλά in verse 17, we also noted earlier that the Greek sentence in verse 14 is constructed differently from its Hebrew counterpart. The Masoretic text successively contains a term (הָעַלְמָה) which can be read either as a verb or an adjective, a finite verb (הָרָה), and a participle (יֹלֶדֶת). If הָעַלְמָה is taken as a verb, then it should be translated as “is pregnant.” This meaning will make more sense by taking into account the present aspect provided by the participle (יֹלֶדֶת). If one considers הָעַלְמָה as an adjective, then it would still bear a present connotation as it is governed by the meaning of the participle (יֹלֶדֶת). In either case, the sentence structure seems to describe the situation of the woman in question: at the moment the statement is made, she is already pregnant and in fact on the point of giving birth. However, in the LXX, three coordinate verbs are used, all of them in the future tense (ἐλεύσεται ... καλέσεις ... καλέσει), thus constructing the sentence to refer to the near future. Even if “the presence of הִנֵּה at the opening of the verse would call for a futuristic interpretation of [the copula],” as de Sousa has argued, it is worth noting, as Brown has correctly pointed out, that “while ... the Hebrew is vague about whether the conception had already taken place or would take place in the future, the Greek is not vague and the conception is definitely future” ..."
Ngunga, Abi T. Messianism in the Old Greek of Isaiah: An Intertextual Analysis (pp. 80-81) Vandenhoeck & Ruprecht, 2013