en_tn_lite_do_not_use/2sa/15/20.md

why should I make you wander all over with us?

This rhetorical question emphasizes David did not want Ittai to come. This question can be translated as a statement. Alternate translation: "I do not want to cause you to wander around with us." (See: rc://en/ta/man/translate/figs-rquestion)

Since you just left yesterday

Here "yesterday" is an exaggeration that emphasizes a short amount of time. Ittai the Gittite had lived there for several years. Alternate translation: "Since you have lived here only a short time" (See: rc://en/ta/man/translate/figs-hyperbole)

may steadfast love and faithfulness go with you

This is a blessing that David is giving to him. The abstract nouns "love" and "faithfulness" can be expressed with the verb "love" and the adjective "faithful." Alternate translation: "may Yahweh love you without ceasing and be faithful to you" (See: rc://en/ta/man/translate/figs-abstractnouns)