The subdeacon has no right to wear an orarium [i.e., stole], nor to leave the doors.
Ancient Epitome of Canon XXII.
A subdeacon must not wear an orarium nor leave the doors.
The “orarium” is what we call now the stole.
In old times, so we are told by Zonaras p. 141 and Balsamon, it was the place of the subdeacons to stand at the church doors and to bring in and take out the catechumens and the penitents at the proper points in the service. Zonaras remarks that no one need be surprised if this, like many other ancient customs, has been entirely changed and abandoned.
This canon is found in the Corpus Juris Canonici, Gratians Decretum, Pars I., Dist. xxxii., canon xxvij., but reads hostias instead of ostia, thus making the canon forbid the subdeacons to leave the Hosts; and to make this worse the ancient Glossator adds, “but the subdeacon should remain and consume them with the other ministers.” The Roman Correctors indeed note the error but have not felt themselves at liberty to correct it on account of the authority of the gloss. Van Espen remarks “To-day if any Hosts remain which are not to be reserved, the celebrant consumes them himself, but perchance in the time the gloss was written, it was the custom that the subdeacons and other ministers of the altar were accustomed to do this, but whenever the ministers present gradually fell into the habit of not receiving the sacrament, this consumption of what remained devolved upon the celebrant.” 194
It is interesting to note that the ancient custom is in full use in the Anglican Church today, ordered expressly by the rubrics of the Prayer Book.