Nicene and Ante-Nicene Fathers, Ser. II, Vol. XIV:
Early Church Fathers
The Canons of the Council in Trullo; Often Called The Quinisext Council.: Canon LXXVIII
It behoves those who are illuminated to learn the Creed by heart and to recite it to the bishop or presbyters on the Fifth Feria of the Week.
Ancient Epitome of Canon LXXVIII.
He that is illuminated is to recite (ἀπαγγελλέτω ) the faith on the fifth feria of the week.
This is a renewal of canon xlvi. of Laodicea.
Next: Canon LXXIX