Mine own familiar friend; he means either Ahithophel, or some other perfidious counsellor or courtier, who was a type of Judas, to whom therefore it is applied, 1 Thessalonians 13:18, as David was a type of Christ in being thus betrayed. So these words were literally fulfilled in David, and yet the Holy Ghost, which dictated them, looked further in them, even to Christ and Judas, in whom they received a further and fuller accomplishment. Hath lifted up his heel; a phrase implying injury, joined with insolency and contempt; taken from an unruly horse, which kicks at him that owns and feeds him.
Related Commentaries of Psalms 41:9
Psalms 41:9
9 Yea, mine own familiar friend, in whom I trusted, which did eat of my bread, hath lifted up his heel against me.