Compassest. — There is some obscurity about this word. The Hebrew verb means first to scatter, and is used of throwing corn about to winnow it (Isaiah 30:24; Jeremiah 4:11; Ruth 3:2). Hence by an easy metaphor it may mean to sift or search out. The LXX. and Theodotion, followed by the Vulg., have traced, investigated. Jerome has winnowed. The Authorised Version rendering appears to come from a mistaken etymology.
A most plausible suggestion connects the verb with zûr, to lodge, which makes a perfect parallelism with the verb to dwell, in the next clause. Literally,
About my path and bed thou art a guest,
In all my ways thou dwellest;
i.e., art as familiar with all my life as one inhabiting the same house could be.
My path. — Literally, my going.