This is the 2685th most frequent Chinese word.
乎
"乎" is a particle used for questioning, exclamation, or indicating location/direction in classical Chinese.
In this context, '乎' is used as a modal particle indicating a rhetorical or inquisitive tone at the end of a question.
人欲而不知其所求乎？
Does a person desire without knowing what he seeks?
Here, '乎' indicates 'with respect to' or 'in reference to,' modifying the word '时' (time).
吾心动乎时而不拘于形。
My heart moves with time and is not constrained by form.
In this sentence, '乎' marks the topic or subject being referred to, emphasizing '彼' (him).