Due to several causes, blindness was common in the ancient world. The blind were one of the groups to whom special protection was due; it was true piety to help them (Job 29.15) and a severe violation to mislead them (Lev. 19.14; Deut. 27.18). Blindness was a ritual blemish: the blind could not function as priests (Lev. 21.18), nor could blind animals be offered in sacrifice (Lev. 22.22; Deut. 15.21; Mal. 1.8). Although blindness was attributed to various physical causes, including old age (1 Kings 14.4; cf. Gen. 27.1; Deut. 34.7) and trauma (Tob. 2.10), it could be interpreted as divine punishment (Deut. 28.28; John 9.2). In the Gospels, healing the blind is one of the characteristic activities of Jesus (Matt. 9.27–30 par.; 11.5; 21.14; Mark 8.22–25; John 9.1–7), and it was interpreted as a messianic sign (Matt. 11.4 par.; Luke 4.18–21; see Isa. 35.5; 61.1–2).
Blindness is also used metaphorically throughout the Bible. Isaiah 6.9 is a classical illustration, taken up repeatedly in the New Testament (Matt. 13.13–15 par.; John 12.39–41; Acts 28.26–27). The Pharisees are denounced in Matthew 15.14 as “blind guides of the blind” (cf. John 9.40–41), but for the author of the gospel of John, Jesus is the “light of the world” (8.12), that helps the blind see but can also blind the sighted (9.39).