It does not mean concealing in a dishonest way, it means hides it, keeps it out of view, covers it, does not say everything he could say. Those who really love knowledge do not love it for the praise it brings them from men, but for its own sake.
Here is an insight into words. What is our objective? Now of course, we are friends, and we are entitled to say many light things to each other, happy things, general observations. We are entitled to enjoy all manner of subjects together. Yes, but there are the higher things: what am I here for in life? At the office, my place of business, among the students, in my family, among the Lord's people, what is the highest and the best thing which I must never let go of? It is to pass on the benefit others have given me, or the Lord has given me. What matters is not showing people how much I may know, but just that word in season, just that help which is needed, just so much. Knowledge is not for self-exhibition, it is for God's sake, to communicate some truth; that is what counts.