LXX Isaiah 7:14
12 But Achaz said, I will not ask, nor will I put the Lord to the test. 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. 16 For before the child knows good or bad, he defies evil to choose what is good, and the land that you fear from before the two kings will be abandoned.
Matthew 1:23
21 She will give birth to a son and you will name him Jesus because he will save his people from their sins.” 22 This all happened so that what was spoken by the Lord through the prophet would be fulfilled: 23 “Look! The virgin will conceive and give birth to a son, and they will name him Emmanuel,” which means “God with us.” 24 When Joseph awoke from sleep he did what the angel of the Lord told him. He took his wife, 25 but did not have marital relations with her until she gave birth to a son, whom he named Jesus.
Notes and References
"... By quoting the text, the narrator "forces" the reader to "listen" to the Jesus-story in light of the promised "Emmanuel". We have here a clear form of reader guidance. By giving an explicit text (Is 7.14), the narrator unfolds a dynamic reading that is difficult to control. The "intrusion" of the old text into a new literary context may induce the reader to reflect and meditate on possible interconnections. Some ambiguities of the Hebrew version are absent in the Greek text. 67 A vague messianic understanding can be glimpsed in the way the child is introduced. Unlike the Hebrew text, the Greek highlights the distinctive character of the child in a very specific way: he has the ability to distinguish good from evil before he knows either (LXX Is 7.15-16). As Martin Rosel has pointed out, the Septuagint version implies an understanding of the child as a heavenly gifted figure. 68 Although other textual elements from the Isaiah context may enrich the interpretation of the Matthean narrative,69 the narrator makes sure that no reader misses the main point: the narrative makes Scripture "complete" ..."
Mayordomo, Moisés "Matthew 1-2 and the Problem of Intertextuality" in Claire Clivaz, et al. (eds.), Infancy Gospels. Stories and Identities (pp. 272-273) Mohr Siebeck, 2011
"... Matthew’s rendering of the LXX’s parthenos from Isa 7.14 ('A virgin will conceive and bear a son' [Mt 1.23]) remains a site of popular piety and scholarly debate. The Hebrew word translated by parthenos in the LXX is ’almah, which is used in the Tanakh in Isa 7.14 and six other times (Gen 24.43; Ex 2.8; Ps 68.26; Prov 30.19; and Song 1.3; 6.8) in the sense of “a young woman” but does not necessarily suggest “virgin.” The Greek parthenos does not, for the LXX, necessarily connote “virgin,” although that is the predominant translation. It appears in Gen 34.3 in reference to Dinah, who had just had intercourse with Shechem. The Hebrew term betulah, used more than fifty times, including several times in Isaiah, usually (but not always) carries the technical sense of “virgin.” Thus for the Hebrew text of Isa 7.14, and perhaps even the Greek text, the prophet is saying, “The young woman is pregnant” There is no reason to presume her pregnancy was miraculous ..."
Levine, Amy-Jill & Brettler, Marc Zvi The Jewish Annotated New Testament (p. 4) Oxford University Press, 2011