Augustine of Hippo — as excerpted in the Catena Aurea on Matthew 5:38-42

“(de Mendac. 15.) The things which are done by the Saints in the New Testament profit for examples of understanding those Scriptures which are modelled into the form of precepts. Thus we read in Luke; Whoso smiteth thee on the one cheek, turn to him the other also. (Luke 6:29.) Now there is no example of patience more perfect than that of the Lord; yet He, when He was smitten, said not, ‘Behold the other cheek,’ but, If I have spoken amiss, accuse me wherein it is amiss; but if well, why smitest thou me? (John 18:23.) hereby shewing us that that turning of the other cheek should be in the heart.”