Matthew 1:21

τέξεται Ἰησοῦν : Mary is about to bear a son, and He is to bear the significant name of Jesus. The style is an echo of O. T. story, Genesis 17:19, Sept [3], the birth of Isaac and that of Jesus being thereby placed side by side as similar in their preternatural character. καλέσεις : a command in form of a prediction. But there is encouragement as well as command in this future. It is meant to help Joseph out of his doubts into a mood of heroic, resolute action. Cease from brooding anxious thought, think of the child about to be born as destined to a great career. to be signalised by His name Jesus Jehovah the helper. αὐτὸς γὰρ … ἁμαρτιῶν αὐτῶν : interpretation of the name, still part of the angelic speech. αὐτὸς emphatic, he and no other. ἁμαρτ., sins, implying a spiritual conception of Israel's need.

[3] Septuagint.