Nicene and Post-Nicene Fathers, Ser. II, Vol. XIV:
The Canons of the Council in Trullo; Often Called The Quinisext Council.: Canon LXXVIII

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.

Notes.

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.