Some versions have "to David when he was at Hebron." You may want to include "when he was at Hebron" if it is present in your national version. (See: [[rc://en/ta/man/jit/translate-textvariants]])
The original meaning of this question is not clear. Possible meanings are 1) Abner had the power to give the land to David. Alternate translation: "This land is mine!" or 2) David is chosen by God to rule the land: Alternate translation: "This land rightfully belongs to you!" (See: [[rc://en/ta/man/jit/figs-rquestion]])
Here "hand" represents Abner's assistance that he is offering to David. Alternate translation: "I will assist you" (See: [[rc://en/ta/man/jit/figs-metonymy]])