“Within the measured and determinant limits of the stadium, the athletes were bound to contend for the prize, which they forfeited without hope of recovery, if they deviated even a little from the appointed course. In allusion to this inviolable arrangement, the Apostle tells the Corinthians: we will not boast of things without our measure. It may help very much to understand this and the following verses, if, with Hammond, we consider the terms used in them as agnostical. In this view of them, the ‘measure of the rule’ alludes to the path marked out and bound by a white line, for racers in the Isthmian games, celebrated among the Corinthians; and so the Apostle represents his work in preaching the gospel as his spiritual race, and the province to which he was appointed as the compass or stage of ground, which God had distributed or measured out for him to run in. Accordingly, ‘to boast beyond his measure'(ver. 14) and to ‘stretch himself beyond his measure’, refer to one that ran beyond or out of his line. ‘We are come as far as to you’ (ver. 14) alludes to him that came foremost to the goal; and ‘in another man’s line’ (ver.16) signifies ‘in the province that was marked out for somebody else’, in allusion to the line by which the race was bounded, each of the races have the path which he ought to run chalked out to him, and if one stepped over into the other’s path he extended himself over his line.”

-Paxton’s Illustrations (“Manners and Customs”) volume 2