'Frankly' in the Bible

I saw all of it as the activity of God. Frankly, a human being cannot understand what happens on earth, because however hard a man works to discover it, he will not find out. Despite what he thinks he knows, he will not be able to figure it out.

This isn't a large group of people whose speech is unintelligible to you or whose language is difficult for you to comprehend. Frankly, if I had sent you to that kind of people, they would certainly have listened to you!