“of those who deceive me.” The Masoretic Hebrew text reads, “of my heels,” which can be understood in a few different ways. The word “heel” can be understood as “supplanter” (as with “Jacob,” the supplanter, the “heel grabber;” cp. Keil and Delitzsch Old Testament Commentary). Or it can refer to those “at the heels,” those seeking to trip the psalmist up in various ways. Or the Hebrew might have not been copied correctly and a slight emendation would yield readings such as “those who deceive me.” Most critical commentaries on Psalms cover the options in some detail.