"The Conditions for Using!!" (使用の条件!!, Shiyō no Jōken!!, Viz: The Principles of Use!!) is chapter 52 of the original Naruto manga.
Wishing for Sakura to be his girlfriend, Lee vows to defeat her attackers or die trying. Knowing that he can end the battle by using the forbidden Front Lotus, Lee thinks upon his master's stipulations for using the technique: to never use it unless protecting someone precious. Confident that Sakura qualifies, Lee attacks Dosu with the Front Lotus, but Dosu, with Zaku's assistance, survives the attack and strikes Lee.