Canon LVI.
Canons of Local Councils Received Ecumenically (Ancyra, Gangra, Neocaesarea, Antioch, Laodicea) · The Seven Holy Ecumenical Councils
Presbyters may not enter and take their seats in the bema before the entrance of the Bishop: but they must enter with the Bishop, unless he be at home sick, or absent.
LocalE 5.63.2
It is difficult to translate this canon without giving a false idea of its meaning. It does not determine the order of dignity in an ecclesiastical procession, but something entirely different, viz., it provides that when the bishop enters the sanctuary he should not be alone and walk into a place already occupied, but that he should have with him, as a guard of honour, the clergy. Whether these should walk before or after him would be a mere matter of local custom, the rule juniores priores did not universally prevail.
LocalE 5.63.6