If you were looking for a specific play title rather than a quote, you might be thinking of Luigi Pirandello’s play (originally titled Così è (se vi pare) or Right You Are, If You Think You Are ).
One morning, the soldiers captured a young local man named . To the regiment, he was a spy. To Marie, he was the man who had saved her life when she nearly tumbled off a mountain precipice weeks earlier. To save him from execution, Marie stepped forward and declared his bravery to her "fathers." In a whirlwind of mountain air and military pride, she burst into the famous aria, "Chacun le sait" —singing of the 21st’s unmatched glory and how "everyone knows" they are the bravest, most dashing men in France. A Heart Divided chacun le sait pdf better