κενός

Who by the mouth of thy servant David hast said, Why did the heathen rage, and the people imagine vain things?

Beware lest any man spoil you through philosophy and vain deceit, after the tradition of men, after the rudiments of the world, and not after Christ.

Let no man deceive you with vain words: for because of these things cometh the wrath of God upon the children of disobedience.

And I went up by revelation, and communicated unto them that gospel which I preach among the Gentiles, but privately to them which were of reputation, lest by any means I should run, or had run, in vain.

But by the grace of God I am what I am: and his grace which was bestowed upon me was not in vain; but I laboured more abundantly than they all: yet not I, but the grace of God which was with me.

And if Christ be not risen, then is our preaching vain, and your faith is also vain.

Therefore, my beloved brethren, be ye stedfast, unmoveable, always abounding in the work of the Lord, forasmuch as ye know that your labour is not in vain in the Lord.

For yourselves, brethren, know our entrance in unto you, that it was not in vain:

For this cause, when I could no longer forbear, I sent to know your faith, lest by some means the tempter have tempted you, and our labour be in vain.

We then, as workers together with him, beseech you also that ye receive not the grace of God in vain.