'Certain' in the Bible

So then, my brothers, be all the more eager to make your calling and election certain, for if you keep on doing this you will never fail.

And so the words of the prophets are made more certain; and it is well for you to give attention to them as to a light shining in a dark place, till the dawn comes and the morning star is seen in your hearts;

This letter which I am now writing to you, dear friends, is my second letter. In both my letters I seek to revive in your honest minds the memory of certain things,

the Lord is not slow in regard to the promise, as certain count slowness, but is long-suffering to us, not counselling any to be lost but all to pass on to reformation,

And be certain that the long waiting of the Lord is for salvation; even as our brother Paul has said in his letters to you, from the wisdom which was given to him;

as also in all the epistles, speaking in them concerning these things, among which things are certain hard to be understood, which the untaught and unstable do wrest, as also the other Writings, unto their own destruction.