"Greatness knows itself. ..." is a line from which play of William Shakespeare?

William Shakespeare has given us some choice words to live by. When we note people who are called great, there is a line by Shakespeare that is often applied. It is the line "Greatness knows itself." This is from William Shakespeare's play, Henry IV, Part I (c. 1597), Act IV, scene 3, line 74. The line concerns the king and is being said to Sir Walter Blunt by Hotspur (Henry Percy). King Henry IV’s son, Prince Harry (Hal), who is simultaneously a deceitful and heroic man is an archrival of Hotspur.

Hotspur is the son of the Earl of Northumberland; he is a young nobleman who is leading the rebellion against King Henry IV. He is seen as a courageous and impetuous young leader and daring warrior. He's a man who has a "hot" temper, eats enemy soldiers for breakfast, and has a serious thing for 'honor'.

Because of his stubborn nature and overall make up, William Shakespeare's play Henry IV has sent him (Hotspur) on a path to sure destruction. He is well respected by King Henry and is a man almost fit to be called a prince. However, unlike the king, will he ever be fit enough to be called great?