From Zelda Legends Wiki
Nayu's Love is the third and final magic technique learned by Link in Ocarina of Time. Obtained by bombing a crack in a cliff in the desert near the Desert Colossus, Naru's love provides a protecion very similar to the Magic Armor in Wind Waker. Link takes no damage from enemy attacks, but reacts to them as he normally does. The moajor difference between Naru's Love and the Magic Armor is that Link invokes Naru's Love by doing a little dance, and the protection lasts for a set time and then vanishes, consuming magic power only once when it is used. The Magic Armor, however, gives constant protection and continually sucks up magic power.