Terce is the third of the canonical hours. It is the hour in which the Holy spirit descended upon the Apostles at the first Pentecost.
The origin of Terce, like that of Sext and None, to which it bears a close relationship, dates back to Apostolic times. As has already been stated (see NONE) according to an ancient custom of the Romans and Greeks, the day and night respectively were divided into four parts of about three hours each. The second division of the day hours was that of Terce from nine o'clock until midday. These divisions of the day were also in vogue among the Jews at the time of Christ. In the New Testament we find mention of the sixth hour in Matthew 20:5; 27:45; Mark 15:33; John 19:14; of the ninth hour, in Matthew 27:46; Mark 15:25; the Holy Ghost descends upon the Apostles on the day of Pentecost at the third hour, Acts 2:15. Some of these texts prove that these three hours were, in preference to others, chosen for prayer by the Christians, and probably also by the Jews, from whom the Christians appear to have borrowed the custom. We find frequent mention in the Fathers of the Church and the ecclesiastical writers of the third century of Terce, Sext, and None as hours for daily prayers. For example, Tertullian, Clement of Alexandria, and the Canons of Hippolytus (see Clement, "Stromat.", VII, vii, in P.G., IX, 455-458). Tertullian says expressly that we should always pray, and that there is no prescribed time for prayer, but adds: "As regards the time, there should be no lax observation of certain hours--I mean, of those common hours which have long marked the divisions of the day, the third, the sixth, and the ninth--and which we may observe in Scripture to be more solemn than the rest" (On Prayer 25/a>).