“your going out and your coming in.” This is spoken as an idiom and technically is the figure of speech polarmerismos. Polarmerismos occurs when two extremes are used to represent a whole. Here, “going out and coming in” represents the two extremes of life, such as when a person goes out in the morning and comes back in at night. In this context, it means all that you are doing, which is doubled for emphasis in the last phrase of the verse: “know all that you are doing.” Joab was adamant that Abner only came to David to spy on what he was doing and gain an advantage in elevating Ish-bosheth to the throne over Israel.

[For more on polarmerismos, see commentary on Joshua 14:11, and for a similar use of polarmerismos, see 1 Kings 3:7.]