The word euperistaton means literally, "wellstandingaround." But eu in composition often means readily, easily, aptly. Then we may render it, "the readily surrounding sin," that is, the sin which readily surrounds us, and thereby entangle us, so as to prevent as, like long garments, to run our course. The runners threw aside every weight or burden, and also their long garments. These two things seem to have been alluded to. Therefore the second clause is not explanatory of the preceding, as some consider it, but is wholly a distinct thing; there was the burden and the readily entangling sin. The burden was probably worldly cares, or as Theophylact says, "the baggage of earthly concerns;" and the easily encircling sin seems to have been the fear of persecution as Doddridge suggests; which, if allowed to prevail, would lead them to apostasy.
If the word be taken in an active sense, then what is meant is the deceptive power of sin, it being that which readily surrounds and allures us; but if it be taken passively, then what is specifically meant is, that the sin referred to is that which stands fairly and plausibly around us; for "wellstandingaround" is what presents on every side a fair and plausible appearance. And apostasy might have been so represented; for the Jews could produce many plausible arguments. Scapula says that aperistatos is applied by the Greek rhetoricians to a question barely or briefly stated, unaccompanied with any circumstances; then, if instead of the negative, eu, well, be prefixed to it, the meaning would be that it is something well stated and plausibly represented. The version in this case would be, "the sin that plausibly presents itself" If this meaning be received, then there seems to be a striking contrast in the passage; we are surrounded by a throng of witnesses, and also by sin with its plausible pretenses. It is usual with Paul to personify sin.