en_tn/deu/10/16.md

Therefore

"Because of this"

circumcise the foreskin of your heart

The word "foreskin" refers to the fold of skin on a man's private parts that is removed during circumcision. Here Moses is referring to a spiritual circumcision. This means the people must remove the sin from their lives. (See: rc://en/ta/man/jit/figs-metaphor)

no longer stiffen your necks

The phrase "stiffen your necks" is a metaphor that indicates that the people were stubborn, and God wanted them to stop being stubborn. Alternate translation: "stop being stubborn" (See: rc://en/ta/man/jit/figs-metaphor)