The earliest extra-biblical directions for baptism, which occur in the Didache (c. 100), are taken to be about baptism of adults, since they require fasting by the person to be baptised. However, inscriptions dating back to the 2nd century which refer to young children as "children of God" may indicate that Christians customarily baptised infants too. The earliest reference to infant baptism was by Irenaeus (c. 130–202) in his work "Against Heresies". Due to its reference to Eleutherus as the current bishop of Rome, the work is usually dated . Irenaeus speaks of children being "born again to God." This reference has been described as "obscure." Three passages by Origen (185–c. 254) mention infant baptism as traditional and customary. While Tertullian writing c. 198–203 advises the postponement of baptism of little children and the unmarried, he mentions that it was customary to baptise infants, with sponsors speaking on their behalf. The Apostolic Tradition, sometimes attributed to Hippolytus of Rome (died 235), describes how to perform the ceremony of baptism; it states that children were baptised first, and if any of them could not answer for themselves, their parents or someone else from their family was to answer for them.