bébaios

For this cause it is of faith, that it may be according to grace; to the end that the promise may be sure to all the seed; not to that only which is of the law, but to that also which is of the faith of Abraham, who is the father of us all

The first tagged occurrence in Romans.

For if the word spoken through angels proved stedfast, and every transgression and disobedience received a just recompense of reward;

The first tagged occurrence in Hebrews.

Wherefore, brethren, give the more diligence to make your calling and election sure: for if ye do these things, ye shall never stumble:

The first tagged occurrence in 2 Peter.