'Ground' in the Bible

hunted down and persecuted, but not deserted [to stand alone]; struck down, but never destroyed;

We are not again commending ourselves to your favour, but are furnishing you with a ground of boasting on our behalf, so that you may have a reply ready for those with whom superficial appearances are everything and sincerity of heart counts for nothing.

But I will persist in the same line of conduct in order to cut the ground from under the feet of those who desire an opportunity of getting themselves recognized as being on a level with us in the matters about which they boast.