Antioch - Canon 17

If any one having received the ordination of a bishop, and having been appointed to preside over a people, shall not accept his ministry, and will not be persuaded to proceed to the Church entrusted to him, he shall be excommunicated until he, being constrained, accept it, or until a full synod of the bishops of the province shall have determined concerning him.

At first read someone might wonder why someone would show the desire and perform the necessary prerequisites in order to be an overseer, then turn away from his assignment.  Some possibilities come to mind:

1.	The assignment is in an unacceptable region, away from familiar surroundings. This seems to be the least likely reason since the overseer would have made a firm commitment to the Lord's leading early in the process.
2.	The overseer has sought the position from pride and is now exhibiting that trait.  Perhaps the assignment is beneath his perceived ability or aspirations.  This possible scenario can be questioned on the basis of demonstrated humility over an extended period of time.  How could someone working toward the position of overseer mask the pride, unless it might have entered later on.
3.	There is undiscovered or unrepentant sin which may, if brought to light, disqualify the newly ordained overseer. If this was the case, the penalty for evasive tactics would disqualify, making silence trivial except for conscience sake.
4.	Lastly, there is the possibility of a developed health concern making the assignment difficult or impossible to fulfill.

Whatever the reason, the overseer was to be cast out until such time as he should accept or a synod be convened to review and rule on the matter.