18:12 fast twice a week. The only fast prescribed in the law of Moses was on the Day of Atonement (Lev. 16:29–31; 23:27), though voluntary fasting could accompany prayer (Ps. 35:13), penitence (1 Kin. 21:27), and mourning (2 Sam. 1:12). By the time of Christ, Jewish oral tradition had increased the number of fasts expected of the pious. Fasting can be a useful religious exercise (5:33–35; Acts 13:2, 3), but Jesus roundly condemned the practice when it was seen as a way of meriting God’s favor (vv. 11, 12) or when it became an ostentatious display (Matt. 6:16–18; cf. Is. 58:1–6).