1 Samuel 17:18

The NIV is the only translation which uses the word "assurance" in 1 Samuel 17:18.  This indicates that the word is not being used in the way that the Navigators use the term.

However, I particularly like Matthew Henry's Concise Commentary on the Bible related to this passage.

The link to today's verse and surrounding context is here.

How wise the commentator is to point out that when people do the right thing, it should be no surprise that their motives are questioned. Furthermore, it is typical to be attacked for making decisions based upon integrity and truth.

It is interesting to note that David's arrival at the battleground makes his brothers angry and suspicious.  He must have had a reputation as an annoying, know-it-all little brother.

What's worse, he was entitled to this confident opinion!  This is very difficult for me to accept, because I'm an oldest child.  My younger brother always thought very highly of himself!

If you're curious, a link to Matthew Henry's entire commentary on 1 Samuel 17 is found here.