'Sure' in the Bible

Now therefore, since I've treated you so kindly, please swear in the name of the LORD that you'll also be kind to my father's household by giving me this sure sign:

Be sure to keep a distance of about 2,000 cubits between you and it. Don't come near it, so you can be certain where you're going, since you haven't passed this way before."

At this point, the LORD told Joshua, "Today I'm going to exalt you in the sight of all Israel, so they'll be sure that I'm going to be with you just as I was with Moses.