Dancing
"David, wearing only a linen cloth round his waist, danced with all his might to honour the LORD. And so he and all the Israelites took the Covenant Box up to Jerusalem with shouts of joy and the sound of trumpets."
~ 2 Samuel 6.14-15 GNB
That would have been quite a sight. Not something many leaders would do. Even back then, David's wife, Michal, thought that was foolish. But David did not worry about looking bad. "I was dancing to honour the LORD ... And I will go on dancing to honour the LORD ..." (v21).
Michal saved David's life from Saul. (1 Samuel 19.11-17) David went away into exile and Michal was given away to someone else. (1 Samuel 25.44) After Saul died, David took Michal back. (2 Samuel 3.13-15) David took offense of Michal's words "He exposed himself like a fool in the sight of the servant women of his officials!"
Here David's shortsightedness became visible. Michal's point was not the dancing, but that "he exposed himself" (v20). Her point was that dancing to honour the LORD is good, but do it appropriately.
Why would an internal marital disagreement be recorded here? Maybe to explain v23, "Michal, Saul's daughter, never had any children." Because back then, in their cultural context, not having any children was a huge deal.