“Look.” The Greek word is idou (#2400 ἰδού). The second-person singular aorist middle imperative of eidon (εἶδον; “to see, to look at, to perceive) is ἰδοῦ (note the special accent mark on the “u”). However, when idou has an acute accent (ἰδού) as it does in this verse and many others in the New Testament, it is used as a demonstrative particle to draw our attention to something. To be strictly literal we would stick with translations that retain the meaning of seeing something (“Look!”; “Behold!”; “See!”). But ἰδού was used more idiomatically than literally, and thus would be heard by anyone listening as an attention grabber appropriate to the context, not a command to actually look at something. We do the same thing in English. If someone is being accused of being somewhere he was not supposed to be, he may well say, “Look, I told you I was home, and I was.” In this case, the man does not expect us to see anything just because he said “Look.” In the same way, idou should be translated in ways that are appropriate to the context. Thus it is best translated “Look” if the context is visual, “Listen” if the context is audible, “Pay attention,” etc. It often introduces something new or unusual, or something that requires special attention. In that light, there are contexts in which “consider” would be an appropriate translation (cp. Matt. 10:16).
As with any exclamation meant to get people’s attention, the force and meaning of the exclamation idou would be expressed by the tone and volume of the way it was spoken. Thus there are times such as here in Matthew 1:20 when “Look!” is clearly meant to forcefully grab our attention—an angel just showed up with a message about the birth of the Messiah, and we had better pay attention. On the other hand there are times when the context dictates that it would have been used with less force but still deep meaning. For example, in Matthew 19:27, Peter is reminding the Lord that he and the other apostles have left everything to follow him. It is a gentle reminder, so a harsh attention grabber such as “Pay attention!” would not be an appropriate translation in that context, but perhaps “consider,” or even “remember” (cp. Matt. 28:20). Often the punctuation associated with idou can help express the meaning, there being a difference in force between, “Look,...” and “Look!”
Many translations of the English Bible (cp. NIV, NRSV, HCSB) omit the word, usually on the logic that it is based on an underlying Semitic expression and does not bring meaning to the subject. We disagree, and note that BDAG says that it is “frequently omitted in translation, but with some loss of meaning.” In fact, we agree with Bullinger (Figures of Speech Used in the Bible) that it is the figure asterismos (“indicating;” related to “asterisk”), and calls attention to the subject. This can be seen by simply noting that it is not used in every speech or before every interesting or important event, but is carefully placed and when it does occur it always is appropriate.
“favorably accept.” At this point Joseph would naturally have presumed his wife had been unfaithful. Since Joseph was “righteous” (Matt 1:19), he would be obligated to put her away and not take her to himself after she had been “defiled” (Deut. 24:4; See commentary on Matt. 1:19; “and yet”). In this context the angel appears and tells Joseph not to fear to paralambanō (#3880 παραλαμβάνω) his wife. This word is usually translated “take” or “receive,” but can also have the meaning of accept favorably: “Sometimes the emphasis lies not so much on receiving or taking over, as on the fact that the word implies agreement or approval, accept” (BDAG). Hence, the angel is assuring Joseph that he may accept his wife, not fearing any defilement. Additionally, the word would come with the strong connotation of “taking to one’s self” or receiving Mary into his house (as in Matt 1:24).
“the Holy Spirit.” “The Holy Spirit” is the name for God that emphasizes His power in operation. God is called “the Holy Spirit” in a number of verses in the NT, including Matthew 1:20; 12:32; and Hebrews 9:8. In this case, there is not a definite article before “Holy Spirit” due to the preposition ek is before the phrase making the definite article unnecessary. [For more information on the uses of “Holy Spirit”, see Appendix 6: Usages of ‘Spirit’]