Easton's Bible Dictionary: M. G. Easton, M.A., D.D.
Smiting on the cheek was accounted a grievous injury and insult (Job 16:10; Lam. 3:30; Mic. 5:1). The admonition (Lk. 6:29), "Unto him that smiteth thee on the one cheek offer also the other," means simply, "Resist not evil" (Mt. 5:39; 1 Pet. 2:19-23). Ps. 3:7 = that God had deprived his enemies of the power of doing him injury.