Ildefonsus was from the Toletan family. As a youth he was educated in the monastery of Agali, then he was ordained a deacon in Toledo by the Bishop Helladius (he writes about these events in his own work De viris illustribus). In 657, after the death of Eugenius II, Ildefonsus became a bishop of Toledo at the instigation of King Reccesvinth (reigned 653-672). He died in 667. He wrote De cognitione baptismi during his episcopacy. Along with the passage 2.21-27 from Isidore`s of Seville De officiis it is the most important document of the baptismal practice in the 7th c. Spain. For more detailed information on the text see Robles 1970, and Yarza Urquiola 278-333.