Why does the wicked magician need Aladdin to get the lamp?

The wicked magician needs Aladdin to retrieve the lamp because it is hidden within a magical cave that can only be accessed by someone pure of heart, which Aladdin is. The magician, who covets the lamp's powerful genie, manipulates Aladdin into entering the cave and obtaining the lamp for him. By using Aladdin as a pawn, the magician seeks to harness the genie's powers for his own selfish purposes without risking his own safety.