He calls the “soles of their feet” the products of their journeys, in order to say that the impious are not prosperous in their travels when they fall into “a violent ruin.” But also their fruits of season, that is, their children, are insatiately consumed by death; and from this entire condition, in which they find themselves, all healing withdraws. That is, their results will always be incorrigible and incurable. It is also possible to interpret the “soles of their feet” as their offspring or descendants.
Source: COMMENTARY ON JOB 18:12-14