In which of these ways the threefold interrogation (“usitata et legitima verba interrogationis”) was made at Jerusalem, is not quite certain from Cyril’s words:  “Each was asked, Dost thou believe in the name of the Father, and of the Son, and of the Holy Ghost, and ye made that saving confession, and went down thrice into the water Mystag.  iii. § 4..”  The Didaché Cap. vii. enjoins baptism simply into the names of the Three Persons of the Holy Trinity.  Justin Martyr Apolog. I. c. adds a few words only to the names “of God the Father and Lord of the universe, and of our Saviour Jesus Christ, and of the Holy Spirit;” and Tertullian De Baptismo, c. vi. observes that “Wherever there are three, that is, the Father, the Son, and the Holy Spirit, there is the Church, which is a body of three.”  The trine immersion had reference not only to the Trinity, but was also a symbol of the three days of our Saviour’s burial Mystag. ii. § 4, note 3..  The use of the three Holy Names was made more strictly indispensable as heresies were multiplied:  thus the 49th Apostolic Canon, which, Hefele says, “must be reckoned among the most ancient Canons of the Church,” orders that “If any Bishop or Presbyter does not baptize, according to the Lord’s command, into the Father, the Son, and the Holy Ghost, but into three Beings without beginning, or into three Sons, or three Comforters, he shall be deprived.”