OET interlinear 2 SAM 18:21

uW Translation Notes:

Note 1 topic: figures-of-speech / explicit

לַ⁠כּוּשִׁ֔י

(Some words not found in UHB: and=he/it_said Yōʼāⱱ/(Joab) to,Cushite go tell to/for=the_king which/who seen and,he_bowed_down Kūshiy/(Cushite) to,Joab and,he_ran )

The author assumes that his readers will know that by the Cushite, he means a particular man from the region of Cush (modern Ethiopia) who was able to run far and fast and so served Joab as a messenger. You could say that explicitly if that would be helpful to your readers. Alternate translation: [the Cushite man who served him as a swift messenger]

Note 2 topic: translate-symaction

וַ⁠יִּשְׁתַּ֧חוּ כוּשִׁ֛י לְ⁠יוֹאָ֖ב

(Some words not found in UHB: and=he/it_said Yōʼāⱱ/(Joab) to,Cushite go tell to/for=the_king which/who seen and,he_bowed_down Kūshiy/(Cushite) to,Joab and,he_ran )

Bowing down before Joab was a symbolic action by which the Cushite showed his respect and submission to Joab’s authority to indicate that he would obey Joab’s command. If it would be helpful to your readers, you could explain the significance of this action in the text of your translation or in a footnote. Alternate translation: [And the Cushite expressed his obedience to Joab]