Other source:

As soon as Piccolo increases his size again Goku jumps down his throat to retrieve the swallowed Denshi jar, saving Kami. Realizing he was tricked, Piccolo returns to his normal size. As they continue battling, Kami jumps in to protect Goku from a punch. Goku says he wants to fight alone and allows Piccolo to redo the punch. As the battle continues, Piccolo resorts to using his ultimate attack.