rest upvi phrasalphrasal verb, intransitive: Verb with adverb(s) or preposition(s), having special meaning and not taking direct object--for example, "make up" [=reconcile]: "After they fought, they made up."
informal (take time to recover)
（使）充分休息 shǐ chōng fèn xiū xī
After climbing that mountain, I had to rest up for three days! After his accident, he needed a few days to rest up and regain his strength.