DB Chapter 295
From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
"The Assimilation" (おもいがけぬスーパーパワーアップ, Omoigakenu Sūpā Pawā Appu; Literally meaning "An Unexpected Super Power-Up") is chapter 295 of the Dragon Ball manga.
Piccolo notes that he's on the brink of death. Nail realizes this must be the Namekian the Earthlings spoke of, and is glad they've had their wish granted. Piccolo thinks this person must know all about the current circumstances, but says he must go help. Nail says that if he returned to his original state as a single true Namekian, he could probably defeat Freeza. Piccolo asks if he means assimilating with that damned God would mean his strength would surpass Freeza's, and Nail says yes, explaining that he knows just how strong Freeza is. Piccolo says he can't do that now, and even if he could, he wouldn't want to rejoin with him anyway.
Nail says he should assimilate with him instead, the only Fighting-Type Namekian. He says Piccolo's power would grow exponentially, but Piccolo has to refuse the offer, as he wants to stay himself. Nail says there's no time, and to put his hand to his body, explaining not to worry as his personality won't change. Piccolo says he's lying, and Nail says, "If you think that, go as you are now, and get killed by Freeza if you like..." Piccolo reluctantly agrees, but threatens to throw him out if he doesn't like it. Nail insists it's just a present, and he should definitely be able to defeat Freeza. Nail suddenly starts flashing, and is absorbed into Piccolo. Piccolo catches his breath, and then, "What power...!! An unbelievable degree of tremendous power...!!! Is this what 'assimilation' is...!!! I can win!!! No matter who my opponent is, I shouldn't be able to lose!!! I have now attained ultimate power!!!" And with that, Piccolo flies off laughing with delight.
Meanwhile, Freeza continues powering up, but stops to ask if the three ants think they can win against a dinosaur. Vegeta says he can win, somehow or other with these three. Freeza laughs, but Vegeta explains about his deep hidden power, and that he's approaching becoming a Super Saiyan. Freeza simply laughs at Vegeta, then suddenly gets mad and charges at Vegeta. Vegeta catches his fist, though, and then the other fist. Vegeta holds him off like that until Freeza's scouter explodes, and they finally break apart. Freeza realizes he needs to get serious after all, as Kuririn and Gohan if they can actually help Vegeta. But then Vegeta tells Freeza to transform and show them his true form. Freeza wonders how he knows about that, and Vegeta explains that Zarbon spat it out. "Well alright...!! If you want to die that much, I'll show you!!!"