A Christian martyr is a person who is killed for following Christianity, through stoning, crucifixion, burning at the stake or other forms of torture and capital punishment. The word "martyr" comes from the Greek word μάρτυς, mártys, which means "witness." At first, the term applied to Apostles. Once Christians started to undergo persecution, the term came to be applied to those who suffered hardships for their faith. Finally, it was restricted to those who had been killed for their faith. The early Christian period before Constantine I was the "Age of martyrs". A martyr's death was considered a "baptism in blood," cleansing one of sin, similar to the effect of baptism in water. Early Christians venerated martyrs as powerful intercessors, and their utterances were treasured as inspired by the Holy Spirit.