OET interlinear ISA 28:21

uW Translation Notes:

Note 1 topic: grammar-connect-logic-result

כִּ֤י כְ⁠הַר פְּרָצִים֙ יָק֣וּם יְהוָ֔ה כְּ⁠עֵ֖מֶק בְּ⁠גִבְע֣וֹן יִרְגָּ֑ז לַ⁠עֲשׂ֤וֹת מַעֲשֵׂ֨⁠הוּ֙ זָ֣ר מַעֲשֵׂ֔⁠הוּ וְ⁠לַֽ⁠עֲבֹד֙ עֲבֹ֣דָת֔⁠וֹ נָכְרִיָּ֖ה עֲבֹדָתֽ⁠וֹ

that/for/because/then/when like,the_mountain_of Pərāʦīm rise_up YHWH like,a_valley in,Gibeon rage for=doing deed_of,his strange deed_of,his and,to,work work_of,his alien work_of,his

The word translated as For indicates that what follows is a reason for what came before. Use a connector in your language that makes it clear that what follows is a reason for what came before. Alternate translation: [This is because]

Note 2 topic: figures-of-speech / simile

כְ⁠הַר פְּרָצִים֙ יָק֣וּם יְהוָ֔ה כְּ⁠עֵ֖מֶק בְּ⁠גִבְע֣וֹן יִרְגָּ֑ז

like,the_mountain_of Pərāʦīm rise_up YHWH like,a_valley in,Gibeon rage

The point of this comparison is that just as Yahweh will arise as at Mount Perazim and he will rage as in the Valley of Gibeon in past battles, so he will act powerfully now in judgment against his own people. If it would be helpful in your language, you could make this point explicitly. Alternate translation: [Yahweh will arise just as he did at Mount Perazim and will rage just as he did in the Valley of Gibeon]

Note 3 topic: translate-names

כְ⁠הַר פְּרָצִים֙

like,the_mountain_of Pərāʦīm

The word Mount Perazim is the name of a place where Yahweh enabled David to defeat the Philistines (see 2 Samuel 5:20).

Note 4 topic: writing-poetry

לַ⁠עֲשׂ֤וֹת מַעֲשֵׂ֨⁠הוּ֙ זָ֣ר מַעֲשֵׂ֔⁠הוּ וְ⁠לַֽ⁠עֲבֹד֙ עֲבֹ֣דָת֔⁠וֹ נָכְרִיָּ֖ה עֲבֹדָתֽ⁠וֹ

for=doing deed_of,his strange deed_of,his and,to,work work_of,his alien work_of,his

Isaiah is using a construction in which a verb and its object come from the same root. You may be able to use the same construction in your language to express the meaning here. Alternatively, your language may have another way of saying this. Alternate translation: [to accomplish his work—his strange work—and perform his deed—his foreign deed]

Note 5 topic: figures-of-speech / parallelism

לַ⁠עֲשׂ֤וֹת מַעֲשֵׂ֨⁠הוּ֙ זָ֣ר מַעֲשֵׂ֔⁠הוּ וְ⁠לַֽ⁠עֲבֹד֙ עֲבֹ֣דָת֔⁠וֹ נָכְרִיָּ֖ה עֲבֹדָתֽ⁠וֹ

for=doing deed_of,his strange deed_of,his and,to,work work_of,his alien work_of,his

See how your translation team has decided to represent pairs of clauses in Hebrew poetry that mean basically the same thing. Alternate translation: [to do the strange thing he must do] or [to judge his own people in the way that he treated enemies in the past]