'Sure' in the Bible

In this way our testimony about Christ was confirmed and established in you,

(Oh yes, I also baptized the family of Stephanas. Beyond that, I'm not sure whether I baptized anyone else.)

For how do you know, wife, whether you will save your husband [by leading him to Christ]? Or how do you know, husband, whether you will save your wife [by leading her to Christ]?

Therefore let the one who thinks he stands firm [immune to temptation, being overconfident and self-righteous], take care that he does not fall [into sin and condemnation].

You are giving thanks well enough [in a way that God is glorified], but the other person [who does not understand you] is not edified [and spiritually strengthened since he cannot join in your thanksgiving].

Every day I am in danger of death! This is as sure as my boasting in you, which I have in Christ Jesus our Lord.