Albert Barnes Commentary 2 Samuel 16:9

"Then said Abishai the son of Zeruiah unto the king, Why should this dead dog curse my lord the king? let me go over, I pray thee, and take off his head." — 2 Samuel 16:9 (ASV)

This dead dog — See the marginal reference and the note on 2 Samuel 9:8.

Go over — The ravine, possibly with a stream of water (2 Samuel 17:20), that lay between them and Shimei.