Isaiah 40:5

 וְנִגְלָה כְּבוֹד יְהוָה וְרָאוּ כָל-בָּשָׂר יַחְדָּו כִּי פִּי יְהוָה דִּבֵּר

5 And the glory of the LORD will be revealed, and all flesh will see it together. For the mouth of the LORD has spoken.

וְנִגְלָה כְּבוֹד יְהוָה  And the glory of the LORD will be revealed, וְנִגְלָה is a nifal vav-consecutive perfect from גָּלָה, carrying the action of the previous verses along. The question might arise, is this sequential or consequential: it seems best in context to take this as both; the Glory of the Lord, the great כְּבוֹד יְהוָה, is revealed to those who have repented of their sins and await his coming. John's ministry was to do just this, to prepare the people for the coming of their Savior, who appears in the Gospels sort of standing in the back of the crowd gathered around John as he baptized and preached.

Pieper had so much to say about the Glory of the Lord that he did it in a separate monograph. In general, we can take the Glory of the Lord here to be either (1) God's general plan of salvation, or (2) The presence of God in person; as in the moment in which he appeared to Moses. Is this such a specific event? Isaiah appears to be telescoping and speaking in more general terms. This passage is not exclusively about the return from Babylon, nor about Christ's first coming only, or his second coming. The events of God's saving activity among his people can't always be separated in prophesies where more than one of them may be hinted at. I would like to see all of Christ's ministry here--and it certainly is here--but there are Old Testament events which fit the prophet's words as well.

וְרָאוּ כָל-בָּשָׂר  and all flesh will see it, The Mp note says that this phrase occurs twice (cf. Ezekiel 21:4). The verb is a qal vav-consecutive perfect once again, from רָאָה to see. The "flesh" is sometimes a vessel of sin, and sometimes merely a reference to mankind, or mankind as a mortal. Here, all of these apply. Everyone--all flesh--will see the Glory of the Lord. And more than that...

יַחְדָּו  together. The adverb yachdav occurs about 90 times in the Bible and 26 of these are in Isaiah, scattered throughout every part of the book except the historical bridge (it is most rare in prose historical sections). The adverb modifies the verb רָאָה, and tells us that we won't see the Glory of the Lord in a series of personal events, unique to each person, but "together," as a unified humanity. The appearance of Christ was no secret, and Jews and Gentiles, kings and shepherds together bowed down to worship him.

כִּי פִּי יְהוָה דִּבֵּר  For the mouth of the LORD has spoken. The כִּי is causal; this is what God says, and therefore it will take place. The Mp note tells us that this complete phrase, "For the mouth of the LORD has spoken," occurs three times in the Bible. All three are in Isaiah, spanning the whole document: 1:20; 40:5 and 58:14. Micah, always similar in content to Isaiah (a colleague and perhaps a friend) also has the phrase, except that he adds "the Lord of hosts has spoken," כִּי-פִי יְהוָה צְבָאוֹת דִּבֵּר.

A marginal setumah note places a paragraph break after this verse.