John the Baptist wore "a garment of camel's hair" as a means of repentance (Matthew 3:4). As such, adherents of many Christian denominations have worn sackcloth to repent, mortify the flesh or as a penance, especially for sins relating to lavishly adorning oneself (cf. 1 Peter 3:3, 1 Timothy 2:9).

Cilices have been used for centuries in the Catholic Church