DB Chapter 46
From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
"The Final Match" (大決勝戦, Dai-Kesshōsen; Literally meaning "The Grand Finals") is chapter 046 of the Dragon Ball manga.
Kuririn runs out to the ring and celebrates with Goku, but Jackie's not that excited. Namu climbs back into the ring and shakes hands with Goku, congratulating him, and the announcer says there'll be a ten minute break before the finals kick off. Backstage, Namu gathers his things and prepares to leave, disappointed to have to return home empty-handed. Jackie tosses him a capsule, and says he can use this thing to hold a lot of water to take back home. Namu freaks out, and asks how he knows about the water. "I'm Muten Rōshi. I can see through those things."
Namu freaks out, and asks why he's here in disguise. Jackie explains that his two students, Kuririn and Goku, are here. He says they've both exceeded his expectations, especially Goku, who appears to be hiding some unbelievable power. He wants to see the two of them become great martial artists, so he's competing in disguise to show them that the world's a huge place with lots of strong opponents. Namu asks if the hair's a wig, and Jackie says he glued it on, and it itches like crazy. Namu thanks him once again, and says it was an honor speaking with him, but he doesn't have any money to buy water to put in the capsule. Jackie points to a well outside, where he's free to take as much water as he wants. The announcer then calls out Jackie and Goku for the next match. Before he leaves, though, Jackie has a favor to ask of Namu.
The announcer proclaims that it's finally time for the finals of the Tenka'ichi Budōkai. Kuririn cheers on Goku, and Yamcha asks Jackie if he'll lose to his student. Jackie insists he isn't Muten Rōshi, and points to Muten Rōshi in the audience! Yamcha's can’t believe it, but is convinced and goes over to tell Kuririn and Goku that Jackie isn't Muten Rōshi after all. Goku begins wonders that there is another really strong old man out there. Meanwhile, Namu takes off the glasses and the beard that Muten Rōshi gave him and heads off.
Goku and Jackie enter the ring and the announcer is amazed that Goku looks so happy to be fighting Jackie. Goku says he's excited to fight such a strong old man. Goku and Jackie stare each other down. The announcer calls for the finals to begin and Jackie takes off, rushing towards Goku.