Born in Thessaloniki, he was granted to his previously childless parents through their prayers to God. After the death of his father—who had served as the military commander (voivode) of Thessaloniki—Emperor Maximian appointed Demetrius to the same position, specifically instructing him to persecute Christians. However, instead of persecuting them, Demetrius openly professed Christ in Thessaloniki. Upon arriving in the city, the Emperor summoned Demetrius; when the latter confessed his faith in Christ even in the Emperor's presence, he was cast into prison. Knowing what awaited him, Demetrius entrusted all his possessions to his attendant, Lupus, with instructions to distribute them among the poor. While in prison, an angel of God appeared to him and strengthened him. A few days later, by the Emperor's command, soldiers pierced him with spears while he was still in prison. As the patron of Thessaloniki, he has saved the city on many occasions. In Russia, he is regarded as the patron saint of Siberia.
Venerable Martyr Joasaph. Commemoration of the great earthquake in Constantinople.