And you will say in that day: See the comments on Isa 12.1, but here the pronoun you is plural. Verse 4 can be seen as a second beginning of the song in this chapter, but here the audience changes from one person to many.

Give thanks to the LORD: See the comments on Isa 12.1.

Call upon his name is a fixed, figurative expression used in worship. It can refer to prayer, to thanksgiving (as it does here), to lament, or to almost any other liturgical act. Here it may be rendered “praise him” or “make him [or, his name] known.” Bible en français courant translates “say out loud who is God,” and Die Bibel im heutigen Deutsch says “Make his name known everywhere!” New Jewish Publication Society’s Tanakh has “proclaim His name.” Good News Translation “Call for him to help you” seems hardly appropriate in a song of thanksgiving. This line is parallel to the previous one with the sense of “praising the LORD.”

God’s name is not just a reference to the fame or reputation of God but, in Hebrew thought, it also refers to the very being of God.

Make known his deeds among the nations is literally “cause to know by [or, among] the peoples his actions.” The Revised Standard Version rendering places emphasis on God’s deeds, but it is ambiguous since it allows for the understanding that God performed these deeds among the nations. However, among the nations is where the worshipers must proclaim God’s deeds; it is not where he performed them. Revised English Bible‘s focus is correct with “make known among the peoples what he has done” (similarly Good News Translation, New Jerusalem Bible, New International Version). His deeds is a summary for all that God will have done in rescuing his people from exile. The nations in Revised Standard Version (also Good News Translation, Contemporary English Version, New International Version, Die Bibel im heutigen Deutsch) limits the meaning of the Hebrew term here (literally “the peoples”; so Revised English Bible) to the foreign nations, as in 11.10. But here it could refer to both Israel as well as the other nations. Bible en français courant is helpful with “all the world.”

Proclaim that his name is exalted is literally “cause [them] to remember that exalted is his name.” Again, his name refers to both God himself and his reputation. The idea that God is exalted carries with it the sense that he is praised and honored. Die Bibel im heutigen Deutsch has “tell them [the nations] how incomparably great he is.” Another possible rendering is “let them remember that he is great.”

Some translation suggestions for this verse are:

• At that time you [plural] will say, “Thanks be to Yahweh! Worship him!
Let the peoples know what he has done;
let them remember that he is honored!

• At that time you [plural] will say, “Praise Yahweh, call upon him by name;
explain to the peoples what he has done,
let them recall how great he is [or, that he is great]!

Quoted with permission from Ogden, Graham S. and Sterk, Jan. A Handbook on Isaiah. (UBS Helps for Translators). New York: UBS, 2011. For this and other handbooks for translators see here .